Forgetful
by Kegler

Ten answers have to be given special treatment before entry into the grid, as indicated by the unclued center entry.
When read in clue order, the first letters of the clues for the ten affected entries describe what the solver is entering.

Forgetful grid

Across
1Rubbed mother's wise friend's back
8Lie next to reflecting instrument
12Remain undecided after dad returns with supplement
14Stooped, as intended, losing bit of stature
15Agile agent obtains core of secrets
17Drink is a place to start, reportedly
18Weird home page describing musician's latest amplifier
19Predictable trace of lisp in scornful expression
20Call a normal stocking “plain”
21Bring in rotten pear
24Hysterically odd wit for survivor of a shipwreck?
25See instructions
29Show's finale rings with cries of excitement
31Northern primate’s back of the neck
32Irate man of the cloth collaring woman of the evening?
34Make an impression with boat after end of week
35Author Anita set off, most relaxed
38No reason, at first, for conjunction
40Lovely festival
41Stooge capturing market for white wine
42Tenor crooner with broken ankle initially tightens wrapping
43Eager newspaperman, carrying on, originally shunned
44Alienate foreign sergeant
Down
1Sam returns top of totem pole
2Papa upset by John while returning horse
3Pair of speakers interpret range
4Provider of funds for one hair product
5Dame shredded cheese
6Guard in back gave instructions to stop
7South China Sea island, distressed about Inga, starting to panic
9Releases pair of ungulates (deer)
10Conk outlaw carrying rifle, finally
11Heard commercials for tool
13Goal I'd bandied about in conversation
16Silly expression about her unoccupied boat
17Prudence rumpled fine T-shirts
19Essayist's breakfast food
22Connecting with lawyer, briefly, hurting
23Leaders of parish's stellar youth choir help cause emotional excitement
26Clean off empty limousine's engine housing
27Agitated Tobin is accommodated by board directly
28Mate, drunk, gulps drop of port
29Cetacean swallowing sole, head to tail, indiscriminately
30“Variety” reader ultimately in disgrace
33Shrink beginning to call one who hasn't paid
35Monk essentially follows medical group
36Embarrassingly boo Ovid's “Shaped Like an Egg”
37Unusual site for stalemates
39Press throw rug and drape, eventually

Solution