Baroque keyboard composition (7)
I believe the answer is:
toccata
'baroque keyboard composition' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for toccata that I've seen before include "Baroque musical piece" , "Baroque keyboard composition" , "Keyboard composition emphasising technique" , "Noted work" , "Series of musical runs and chords before a fugue" .)