During a dim performance (4)
I believe the answer is:
amid
'during' is the definition.
(I've seen this before)
'a dim performance' is the wordplay.
'performance' indicates an anagram.
'dim' with letters rearranged gives 'mid'.
'a'+'mid'='AMID'
(Other definitions for amid that I've seen before include "In the course of" , "'See . . . . the winter's snow' (carol)" , "Among" , "Maid (anag)" , "Amongst" .)