Jazz combo (4)
I believe the answer is:
trio
'jazz combo' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for trio that I've seen before include "Piece for three players" , "Beethoven's 'Archduke', for example" , "Work for three" , "Group of Magi?" , "father, spirit and son" .)