Come Again? by Hotspur Solution

The quotation is "Things fall apart; the centre cannot hold", from Yeats's The Second Coming. Thus the centre letters of each answer (3 ex 5, 2 ex 6, 3 ex 7, 4 ex 8, 3 ex 9, 5 ex 11, 4 ex 12) had to be re-arranged before entry into the grid. Appearing as a spiral in an anti-clockwise direction from the central C of the grid is the phrase CENTRIFUGAL FORCE.

Clues Across:
1. (attached) anag. of SIZE+N+ATACHED (ZANTEDESCHIA)
9. (her) FOR + UM
12. (harim) DY in ILL
13. (tamarind) anag. of PEAS + TAMAR (ASPARTAME)
14. (Bodge) rev. of (N)EAPS
16. (swell) ORD in SO
17. (flock) CLAPS + ILL
19. (Ma) (M)AGNATES
20. (Darnley) anag. (YARNED)
26. (Instal) hidden (TAPETI)
28. (prayer) UN rev. in NOSER
29. (pleading) PROLIFER(ATION)
30. (Brainy) SAL + T(ERR)Y
31. (recce) LO + M + A
33. (at) anag. I + LESSONS + A (SESSIONAL)
34. (Stay) EG in ELY
35. (the) S(E)MI + TE
36. (are) ELL + AR in STATORS
Clues Down:
2. (clot) hidden (i.e. similar colours)
3. (Traverses) odd letters
4. (linens) RIP in STED
5. (table) T + L in DEFY
6. (horse) sound of HIDE RANT
7. (alley) A + HERE in DR
8. (Cruddy) FLO(P) + RID
9. (as) OR + S in FAY
10. (tinnies) rev. of PUT in OC LET
11. (Spurn) anag. of CASINO in PRESS (PROSAICNESS)
15. (let goo) CAN + S + T
18. (Chaste) anag. of N MORAL CERTAINTY minus CLARITY (ORNAMENT)
21. (Mughal) anag. [ambiguity of ALGUM/ALMUG resolved by key phrase]
22. (Bora) anag. A + LIFES plus S (FALSIES)
23. (plan) U + P + SCALE
24. (fund) HO + anag. FUN in R and L
25. (snarly) rev. of GNAR in OE ["jokey" used as red herring for "K" of KEATS]
26. (steel) OR in anag. of STEL
27. (Arnie) anag. of RNIE + OR
31. (sting) (F)LIRT, with L for R
32. (Morse) anag. of MORE