It's All In Your Head

By /u/teamcrazymatt
The twelve Down entries in the six central columns of the grid are one letter too long for their spaces. Before entering them, one letter must be removed from the answer and placed in the gray cell directly above or below that entry. Crossing answers will help you determine which letter needs to be removed. All other entries are entered across/down as normal. When you've finished, the letters in the gray cells will cryptically describe the task you've been completing.
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647
Squares filled: 0/144
Exolve Print Notes Jotter

Across
1Some servants beginning to polish trophies from deer often (8)
9Spoil pound of old fertilizer (4)
13Japanese woman, knockout, chases you and I (5)
14Vixen and coworkers about to tease, "Love you!"? (7)
15Sweetheart left for Japanese theater (3)
16Insane extremists residing in giant town in Senegal (6)
17Have pointed teeth embedded in orangutan's hide (3)
18See me hugging stir-crazy Romanian woman (6)
20Theatre fan's character has ill, vivid makeup (3,3)
21Shrek remake about running noses (7)
23Youth initially with ease uttered quiet expression of disbelief (5)
25Spot of trouble (3)
26What we did to slices of haddock or lamb to become full? (3)
27Even brought back headless puppet bear (3)
28Turned over 37 outlaws' leader to policeman (3)
29You are abandoning most grim old acts (5)
32Violin maker's essentially crisp. Idle? Never (7)
36Chief justice squeezed cut lemon (6)
38One can be adjusted? No it can't (6)
40German man discovered flower (3)
41, 4241, 42Washed Sun editor's convertible (6,3)
42See 41
44Twelfth single drops out of highest point after affair (7)
45Insult, lacking answer, gets Regina extremely excited (5)
46Chuck also has point (4)
47Girl may need rubber Trojan (8)

Down
1Mostly sing with DJ; turn down appearance in small puppet show (5,3,4)
2American love, Spanish love (3)
3Sounded short on soda (4)
4Its baby cats have no eyes, King Tut (3-3)
5Look at the hate (6)
6Rice mixed with a large pastry (6)
7Broadcasts rare goodbye in Spain (6)
8Very much in pain (6)
9Warm disgusting fungus (6)
10Sailor ought to live eating meat from a calf more than anything else (5,3)
11Common arena omission uncovered from watching independent primaries (3,1)
12The uncle's building hosted one-time restaurant (12)
19Round up real numbers, round down constant to zero (5)
22Adapt volume fresh for Bob (8)
24Metal brace (5)
30Painful howl heard at dessert (6)
31Heavily drinking high-quality popular fifth of Carignan (6)
32Selection of words from the Reverend's can-cans? (6)
33Punish free press (4,2)
34North Pole note: "Latest sign of frostbite: Terry's extremities getting number" (6)
35Blasted pop, serving up bash (6)
37Ointment found regularly in mailboxes (4)
39Drill for gold in outskirts of Boise... (4)
43...and in Germany, strip resources (3)