Claim it's a legal fiddle at closing time (6)
I believe the answer is:
allege
'claim' is the definition.
(to allege something is to make a claim)
'a legal fiddle at closing time' is the wordplay.
'fiddle' indicates an anagram.
'at' means one lot of letters go next to another.
'closing time' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'legal' with letters rearranged gives 'alleg'.
'alleg'+'e'='ALLEGE'
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for allege that I've seen before include "Claim, suggest" , "Accuse without established proof" , "Assert, state without proof" , "Declare or accuse without proof" , "Cite in discussion" .)