Musical pair needing sufficient time (4)
I believe the answer is:
duet
'musical pair' is the definition.
(I've seen this in another clue)
'sufficient time' is the wordplay.
'sufficient' becomes 'due' (I've seen this in another clue).
'time' becomes 't' (abbreviation).
'due'+'t'='DUET'
'needing' acts as a link.
(Other definitions for duet that I've seen before include "A song sung by two" , "Performance by two" , "Work for a couple" , "Two singers performing together" , "Piece for brace" .)