Brief moment for twitch (3)
I believe the answer is:
tic
'twitch' is the definition.
(tic is a kind of twitch)
'brief moment' is the wordplay.
'brief' means to remove the last letter (a shorter or briefer version of the word).
'moment' becomes 'tick' (both can mean a very short amount of time).
'tick' with its final letter removed is 'TIC'.
'for' acts as a link.
(Other definitions for tic that I've seen before include "Involuntary contraction" , "Nervous response" , "Convulsive twitching" , "Convulsive spasm" , "Convulsive twitch (of face)" .)