Devil bumping off king in capital? (5)
I believe the answer is:
money
'capital?' is the definition.
(thesaurus)
'devil bumping off king' is the wordplay.
'devil' becomes 'monkey' (both can mean a mischievous child ).
'bumping off' suggests deleting specific letters.
'king' becomes 'k'.
'monkey' with 'k' removed is 'MONEY'.
'in' is the link.
(Other definitions for money that I've seen before include "Cash, notes" , "Mazuma, ackers or dosh" , "Medium of exchange" , "Lucre" , "tin" .)