Finished being entertained by mischievous beggar (10)
I believe the answer is:
impoverish
'beggar' is the definition.
(thesaurus)
'finished being entertained by mischievous' is the wordplay.
'finished' becomes 'over' ('over' can be similar in meaning to 'finished').
'being entertained by' indicates putting letters inside (I've seen this in other clues).
'mischievous' becomes 'impish' ('impish' can be a synonym of 'mischievous').
'over' inserted within 'impish' is 'IMPOVERISH'.
(Other definitions for impoverish that I've seen before include "Make poor" , "Spoil the quality of" , "beggar" .)