Dancing cured Mungo's grump (10)
I believe the answer is:
curmudgeon
'grump' is the definition.
(I've seen this before)
'dancing cured mungo's' is the wordplay.
'dancing' indicates anagramming the letters.
'cured'+'mungo'='curedmungo'
'curedmungo' with letters rearranged gives 'CURMUDGEON'.
(Other definitions for curmudgeon that I've seen before include "Malcontent, grouch" , "Churlish miser" , "Meldrew, say" , "Surly miser" , "He's surly" .)