Occasionally low blow is to finish off player (6)
I believe the answer is:
oboist
'player' is the definition.
(oboe player)
'occasionally low blow is to finish off' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'finish off' means to remove the last letter.
'low'+'blow'='lowblow'
The alternate letters of 'lowblow' are 'obo'.
'to' with its final letter removed is 't'.
'obo'+'is'+'t'='OBOIST'
(Other definitions for oboist that I've seen before include "orchestra member" , "Instrumentalist" , "Wind player" , "Do I boost the musician?" , "Musician who plays woodwind of treble pitch" .)