By Justin Melvin and Dan Collins
Answer: KERNEL

This is the commentary of a person who misinterpreted a variety cryptic crossword as a vanilla crossword. You don’t get to see the cryptic clues, but you do see the definition (in quotes), the answer (all caps), and an oblique clue to how the wordplay works.

The first step is to fill in the grid, which is not provided. The commentary specifies that there is one too many letters for each word, and that the first line begins with a “few black squares”. Using this information, along with the answers (and where they must cross), it is possible to reconstruct the grid as follows:

A R N
Y P P E A H E S
P I L D E A R H
E N E M P E E
G O A L I
T N E Y E L L
R E N D R S K I
P O S T L E E N
S E D

Now that the grid has been identified, it is possible to extract the missing letter from each answer.

Reconstructed clue Definition Wordplay type Answer Answer in grid Letter
Across 1 Acquire a near miss Acquire Anagram EARN ARN E
4 Bark as payback Bark Reversal YAP YP A
6 Preaches without right to fruit Fruit Deletion PEACHES PEAHES C
10 Heard enough of singer Collins Singer Collins Homophone PHIL PIL H
12 Insufficiency of tangled thread Insufficiency Anagram DEARTH DEARH T
13 Yemen mobile’s nemesis Nemesis Anagram ENEMY ENEM Y
15 Glance at Pepe Le Pew Glance Anagram PEEP PEE P
16 Nettender cheers “Go Lee” Nettender Homophone GOALIE GOALI E
18 Animated feature soundtrack’s song Song Homophone TUNE TNE U
20 Jacoby Ellsbury hollers Hollers Hidden word YELLS YELL S
23 Supply in surrender Supply Hidden word RENDER RENDR E
26 Dementor’s kiss for alpine downhill footwear Alpine downhill footwear Anagram SKIS SKI S
27 Religious devotee work in the influence of alcohol Religious devotee Container APOSTLE POSTLE A
29 Fellows of prime numbers Fellows Hidden word MEN EN M
30 Yield to call “nut, for one” Nut, for one Homophone SEED SED E
Down 1 Once around the track backwards, pal Once around the track Reversal LAP AP L
2 Deer inverted bog stick Bog stick Reversal REED RED E
3 Valentina Tereshkova hides silver Silver Hidden word NATE NAE T
4 Style of Katy Perry Style Hidden word TYPE YPE T
5 Tree is spine without scoliosis Tree Deletion PINE PIN E
7 Bird women’s markers lost their caps Bird women Deletion HARPIES HAPIES R
8 Lake I was in before Lake Container ERIE ERE I
9 Man in tin’s League of Legends character League of Legends character Container SHEN SHE N
11 Stories gives an example Stories Container LEGENDS LEGENS D
14 Flaming Moe’s rock style Rock style Anagram EMO MO E
17 Jeff Lynne’s glide Glide Hidden word FLY LY F
18 Journey bottomless: tripe Journey Deletion TRIP TRP I
19 Announcing knee on noble gas Noble gas Homophone NEON NEO N
21 el-Hajj Malik el-Shabazz has similar Similar Hidden word LIKE LKE I
22 Clothing fluff in small intestine Clothing fluff Hidden word LINT LIN T
24 Remove new dints for dashes’ partners Dashes’ partners Deletion DITS DTS I
25 Position of roll call Position Homophone ROLE RLE O
28 Devil’s den’s terminus Terminus Anagram END ED N

This yields the phrase EACH TYPE USE SAME LETTER IN DEFINITION. This means group the clues by wordplay type and select the letter that is in common between each.

Anagrams (7): ACQUIRE, INSUFFICIENCY, NEMESIS, ALPINE DOWNHILL FOOTWEAR, ROCK STYLE, GLANCE, TERMINUS (E)
Reversal (3): BARK, ONCE AROUND THE TRACK, BOG STICK (K)
Deletion (5): FRUIT, TREE, JOURNEY, BIRD WOMAN, DASHES’ PARTNERS (R)
Homophone (6): SINGER COLLINS, NETTENDER, SONG, NUT FOR ONE, NOBLE GAS, POSITION (N)
Container (4): LAKE, RELIGIOUS DEVOTEE, LEAGUE OF LEGENDS CHARACTER, STORIES (E)
Hidden word (8): HOLLERS, SUPPLY, FELLOWS, SILVER, STYLE, GLIDE, SIMILAR, CLOTHING FLUFF (L)

As suggested by the “blanks” diagram in the puzzle, ordering these letters by the frequency of each type yields KERNEL.