Playing clarinet and briefly leaving performance (7)
I believe the answer is:
recital
'performance' is the definition.
(I know that recital is a type of performance)
'playing clarinet and briefly leaving' is the wordplay.
'playing' indicates anagramming the letters.
'and briefly' becomes 'n' (common abbreviation for 'and'; 'briefly' indicates a short form).
'leaving' suggests deleting specific letters.
'clarinet' with 'n' removed is 'clariet'.
'clariet' anagrammed gives 'RECITAL'.
(Other definitions for recital that I've seen before include "Article found in performance" , "Article about musical entertainment" , "Verbal account" , "Concert performance" , "(Usually solo) concert" .)