Piano tune for possible performers of duet (4)
I believe the answer is:
pair
'possible performers of duet' is the definition.
(a duet is performed by two people)
'piano tune' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'tune' becomes 'air' (air can mean a piece of music).
'p'+'air'='PAIR'
'for' is the link.
(Other definitions for pair that I've seen before include "E.g. two aces; mate" , "Brace, couple" , "Husband and wife" , "Cereal used as food" , "2" .)