The answers to the cryptic clues are:

ACROSS

1. CLAMBAKE (anag.)
10. REVEALS (anag.)
17. M AS T
18. BEL+UGA
19. GRIMM (hom.)
22. misERAble
23. ENT+ENT+E
25. C+RIP
26. S(T becomes P)ORKS
28. FORT+“UN-ATE”
29. DI+YER (rev.)
31. URN (hom.)
33. CENTRIPETAL (anag.)
36. fIDO
37. GE(NO)A (anag.)
41. ORBISONGS (anag.)
45. BE(MUS (rev.))E
46. W+A+RM
48. M(Y+CENA)E
50. nOVAk
53. sAUDI+S
54. HATERS (anag.)
55. reTTOP (rev.)
56. SH(AMP)OO
57. DELI+VERY

DOWN

2. LAW+N
3 & 7. ASHTON KUTCHER (anag.)
4. SETTER (anag.)
5. B,E,G
6. AL+IE+N
8. E+GER
9. TA+HIT+I
11. ER(A’S)E
12. VI+M
13. (NI+MROD) (rev.)
14. E(MER)IL (rev.)
15. A+GEN(C)Y
16. SPASm
18. BU(N)T
19. G+APE
20. IR(K)ED (anag.)
21. DEBUG (first letters)
24. TU(N)ES
27. PATS+Y
30. ROLE+X
32. RE+EVE
33. CO(MPAS (anag.))S
34. PIRANHA (anag.)
35. PE(RMU (anag.))TE
36. IGNITE (hid.)
38. NEVADA (anag.)
39. AURUM (hid.)
40. HE+LIO (rev.)
41. ’OWLS
42. IMPEi+L
43. OCHS (hom.)
44. NECTAR (anag.)
45. B(O)Y+S
47. ROAD (hom.)
49. A+M+OR
51. G(D)P
52. sAwRuIn

In order to complete the grid, nine across entries must skip a square, and the intersecting down entries must have two letters entered into those squares.

These across entries all contain the names of types of meat, and the skipped squares fall within each meat. The meats are illustrated next to the grid; these meats are, in order from top to bottom, LIVER, EMU, BISON, LAMB, TRIPE, VEAL, PORK, TUNA, and HAM. (Some of these are admittedly tricky to differentiate just from the pictures. EMU, BISON, and VEAL are arguably the toughest to recognize, but in a worst-case scenario, the solver can just see which arrangement of those three gives a coherent clue phrase.)

Stacking the letters in the skipped squares in the same order as the meats in the image creates a clue phrase reading downward:

In chess, a reverse pin is also called a SKEWER, an appropriate answer for this meat-piercing clue phrase.