Quirk displayed by tailless little insect (3)
I believe the answer is:
tic
'quirk displayed by tailless little insect' is the definition.
'tic' can be an answer for 'quirk' (I've seen this in another clue). I am unsure of the 'displayed by tailless little insect' bit.
'little insect' is the wordplay.
'little' means to remove the last letter (the word is not quite complete).
'insect' becomes 'tick' (I've seen this before).
'tick' with its final letter taken off is 'TIC'.
Can you help me to learn more?
(Other definitions for tic that I've seen before include "Involuntary contraction" , "Regular muscular twitch" , "Involuntary muscular spasm" , "Minor muscle spasm" , "Facial movement" .)