Figure It Out solution
by Kegler

Two letters are removed from each of the ten overlong entries; when connected in clue order, they spell PUT TWO AND TWO TOGETHER.

Figure It Out solution grid

Across
1C + HOW
4PO + P(UL)ARITY
10O(H)AR + A
12PAV(AN)E
13RO(TAR)Y (RAT rev)
14COR(N)EA
15P(R)ETTY
17SE(A)TS
18EROtICA
21ROoSTERS
23AREN + A (NEAR anag)
25SHOW OUT (hidden)
27LI(MI)TER
31DEN + O(V) + O
33T + A(I)GA
35PEST (hidden)
37AN + E + MIA
38SPAN + I + ELS
39END TABLE ("TEND ABEL" spoonerism)
40A[N/r]NIE
41PET(NAM)E'S (MAN rev)
42GrADS
Down
1COW + pORKERS
2H,H + OUR
3W(R)AP + I + TUP (rev)
4PARR ("PAR" hom)
5LA(C)Y
6R + ARE
7INTO + NATE
8TEE + T,H
9Y + EAST
11ATHOS (OATHS anag)
16EAGERL + Y (REGALE anag)
17S(W)AM
19A(S)IDE
20P[R/a]INTING
22E + TNA (rev)
24ARTHOUSES (USE A SHORT anag)
26ORIENT (TENOR I anag)
28T(OK)EN (NET rev)
29ST + AMP (MAP anag)
30RAN + EE
32V(AL)ID
34GERMAN (hidden)
35PAL + M
36SPASm