Drums, monkey stopping to beat one (7)
I believe the answer is:
timpani
'drums' is the definition.
(I've seen this before)
'monkey stopping to beat one' is the wordplay.
'monkey' becomes 'imp' ('imp' can be a synonym of 'monkey').
'stopping' indicates putting letters inside (stopping can mean blocking a gap).
'to beat' becomes 'tan' (I've seen this before**).
'one' becomes 'i' (Roman numeral).
'imp' going within 'tan' is 'timpan'.
'timpan'+'i'='TIMPANI'
(Other definitions for timpani that I've seen before include "orchestra members" , "Percussion instrument" , "Features of kitchen" , "> kitchen equipment?" , "Those beaten" .)