Kaffeeklatsch solution
by Kegler

The eight entries that contain the string HEN squeeze those letters into a single square; 20 Across is HEN PARTY.

Kaffeeklatsch solution grid

Across
1WALDO(RF)'S + A + LAD
9ACH(ENd)E
11I(LIA)'D (AIL rev)
13GEN(TL)E (LT rev)
14S(O-O)TY
15COMP + REH + END (HER rev)
17SA + TRAP (rev)
18GESTE (hidden)
20HEN PARTY
21R(I)OTS
23RA(U)NCH
26ENTHUSED (THE NUDES anag)
28D + OLES
29RUNST + O (TURNS anag)
30FAT + W + A
31T(H)ENET
32THEN + ETHER + L + AND + S
Down
1WAG(E)S
2ACETAMINOPHEN (MENTION A CHEAP anag)
3DE(T)ER
4O + I(LCAN)S (NACL rev)
5FIR(M + WAR)E
6ADORE ("A DOOR" hom)
7AUTHENTICATED (AUNT CHEATED IT anag)
8DRY + DEN
10H + ENNA (rev)
12POE + S,Y
16O + PPO + SITE (POP anag)
18GR + A + DUAL (rev)
19CR(ED)IT
20HOTLY ("LOT HE" spoonerism)
22THE + F,T
24UINTA (hidden)
25sHOOTS
27A(SHE)N