An Evolutionary Question solution
by Kegler
The dropped letters (shown below in red) spell PORK SAUSAGE, the MISSING LINK from 18 Across.
Across
| 1 | IDLES (IS LED anag) |
| 5 | P(ARLO)R |
| 9 | SWANg (rev) |
| 11 | CU(PC + A)KE |
| 12 | AN + T |
| 13 | C + RAM |
| 14 | A + L(ARM + CL)OCK |
| 16 | C(L)OD |
| 17 | WHIR (1st letters) |
| 18 | MISSING LINK |
| 21 | A + NTE (NET anag) |
| 25 | P + ASS |
| 27 | aGREE + N(L)IGHT |
| 29 | THUS (SHUT anag) |
| 30 | NOD (rev) |
| 31 | R(AT + H)OLE |
| 32 | KEy + PT |
| 33 | A(WH)IR + L |
| 34 | RI(N)SE |
|
Down
| 1 | ISAAC (hidden rev) |
| 2 | DO(WELL)ING |
| 3 | LA + RV + A |
| 4 | SCAMP + I |
| 5 | PA(UN)CH (NU rev; CHAP anag) |
| 6 | AP[T/p]LY |
| 7 | L + ARCH |
| 8 | R (EM) + ARK (ME rev) |
| 10 | NE(R)D (DEN rev) |
| 13 | S(C) + OWL |
| 15 | K + INGS + HIPS (SING anag) |
| 18 | MANT(R)A + P |
| 19 | S + EEKS |
| 20 | GUI(L)DE + R |
| 22 | T + RUTH (HURT anag) |
| 23 | TENSOR (STONER anag) |
| 24 | K + NO + L + L |
| 25 | PIN + K (NIP rev) |
| 26 | ESTATE (hidden) |
| 28 | GLEAN (ANGLE anag) |
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