Mock professional clown dropping stone (4)
I believe the answer is:
jeer
'mock' is the definition.
(thesaurus)
'professional clown dropping stone' is the wordplay.
'professional clown' becomes 'jester' (I've seen this before).
'dropping' suggests deleting specific letters.
'stone' becomes 'st'.
'jester' with 'st' taken out is 'JEER'.
(Other definitions for jeer that I've seen before include "Ridicule noisily" , "Call out derisively" , "Mock publicly" , "Tease" , "Scoff, deride, mock" .)