Criminal has no right to fiddle (4)
I believe the answer is:
cook
'fiddle' is the definition.
(thesaurus)
'criminal has no right' is the wordplay.
'criminal' becomes 'crook' ('crook' can be a synonym of 'criminal').
'has no' suggests deleting specific letters.
'right' becomes 'r' (common abbreviation).
'crook' with 'r' taken out is 'COOK'.
'to' acts as a link.
(Other definitions for cook that I've seen before include "Heat food" , "Captain of HMS Endeavour" , "Doctor" , "Falsify - chef" , "18th-century explorer" .)