To closed circuit at a piece of music (7)
I believe the answer is:
toccata
'piece of music' is the definition.
(toccata is a kind of piece of music)
'to closed circuit at a' is the wordplay.
'closed circuit' becomes 'cc' (this could be a standard abbreviation which I don't know about).
'to'+'cc'+'at'+'a'='TOCCATA'
Can you help me to learn more?
(Other definitions for toccata that I've seen before include "Musical composition with rapid elaborate runs" , "Flashy piece of music" , "Baroque keyboard composition" , "lively piece" , "technical challenge" .)