Kettledrums ain’t playing around mischievous fellow (7)
I believe the answer is:
timpani
'kettledrums' is the definition.
(I've seen this before)
'ain't playing around mischievous fellow' is the wordplay.
'playing' indicates an anagram.
'around' indicates putting letters inside.
'mischievous fellow' becomes 'imp' (I am not sure about this - if you are sure you should believe this answer much more).
'aint' is an anagram of 'tani'.
'tani' placed around 'imp' is 'TIMPANI'.
Can you help me to learn more?
(Other definitions for timpani that I've seen before include "Features of kitchen" , "Those beaten" , "PM, I ain't (anag.)" , "Percussion instrument" , "part of kitchen?" .)