Join Us, Won't You? solution
by Kegler

As suggested by 22A's PULL UP A CHAIR, the unclued Down entries are “chairs,” entered bottom to top.

Join Us, Won't You? solution grid

Across
1ELGIN MARBLES (ENLARGE LIMBS anag)
9RO(MA)N
11IN + GA
12OVERT + A + KING
14REtREADS
15S,E + TUP (PUT rev)
18PETROL ("PETREL" hom)
19TRAITS (STRAIT, move the S)
21DELE (hidden)
22PULL UP A CHAIR
24R + IG (GI rev)
25CORIANDER (AND/OR RICE anag)
27FELl + ON
29BAS(T)E
30S(E,E)R
32FLAKe
34TAT + TOO
35I + NUIT (UNIT anag)
37K(N)IT
38I + G + LOO
39GLASS OF WATER (FAR EAST GLOWS anag)
Down
1THRONE “pulled up”
2GOERS (OGRES anag)
3NA(TAN)T
4A(R)KS (ASK anag)
5RAISE (A SIRE anag)
6B + IN
7LOUNGE “pulled up”
8S + AMPLER
10SEDAN “pulled up”
13RECLINER “pulled up”
16T(RE)ADS
17CRUISE (2 defs)
18PLAIN + TIFF
20WINGBACK “pulled up”
22P.R. + Y
23PROBe + ONO
26ROCKER “pulled up”
28STOOL “pulled up”
30STAGe
31ETNA (hidden)
33LI'L + T
36TOE (even letters)