Quintets
by Kegler

Seven of the clues incorporate the otherwise unclued 23 Across.

Quintets grid

Across
1Baby food that is 23 Across beginning to erode classroom building material (6-5)
10Kiss in vehicle, we hear (4)
11At present, the woman's last in line for nonexistent position (7)
13Trapped, ran back inside; needs another way (8)
14Noticing extremists surrounding silent, disturbed young flyer (8)
16Note old black swan (3)
18Emulate policeman starting to yell (4)
20Collection book is approximately 70% white (5)
22Plain one in cottage (7)
23See instructions
26Confused lech may try going for the gold? (7)
29The lizard's cornering Ms. Doolittle (5)
30Pay to play neat composition (4)
31I'm tracing Jack's last name (3)
32Song about 23 Across place to sit (8)
35Incredibly abnormal fish swallowing broken rake (8)
37Circle around net, twisting and tearing (7)
38Flying teal no longer with us (4)
39Trial about 23 Across executor's limits in kangaroo court (4,7)
Down
2Gold ore, refined; note bright glow (7)
3Afterthought is in letters from Greece (4)
4Angry snit ain't correct? (4)
5From speech, sale yesterday returned barely discernible margin (7)
6Starts to miss one's summer months (3)
7Delightful 23 Across in opening of “Gulliver” (8)
8Extraordinarily difficult clue he ran incorrectly (9)
9You and I had married (3)
10Live new 23 Across keeping initial standard of comparison (9)
12Role I play in “Grease”, again (5)
15Erroneously ban professional shooter's organization (3)
17Military leaders at Great Lake cafe (9)
19Shut up about 23 Across diploma (9)
21Freshman's Chem at Annapolis uses outlines (8)
24Attorney retaining 23 Across old Greek capital (7)
25Oversupply I consumed after Saturday (7)
27Stories about one French river (5)
28Edge back from Russian space station (3)
33Remain noncommittal about large steer... (4)
34...near a barn stabling horse (4)
35Young cook (3)
36Elected politician originally cultivates business, briefly (3)

Solution