Chamber group tour finishing early? Over (4)
I believe the answer is:
trio
'chamber group' is the definition.
(I've seen this in another clue)
'tour finishing early? over' is the wordplay.
'tour' becomes 'trip' (I've seen this in another clue).
'finishing early?' means to remove the last letter (the word finishes earlier than normal).
'over' becomes 'o' (cricket abbreviation).
'trip' with its last letter removed is 'tri'.
'tri'+'o'='TRIO'
(Other definitions for trio that I've seen before include "Three together" , "Work for three" , "Ensemble musical piece, eg Beethoven's 'Archduke'" , "father, spirit and son" , "Piece for three players" .)