Claim the lot, for instance, at closing time (6)
I believe the answer is:
allege
'claim' is the definition.
(to allege something is to make a claim)
'the lot for instance at closing time' is the wordplay.
'the lot' becomes 'all' (I've seen this in another clue).
'for instance' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'at' means one lot of letters go next to another.
'closing time' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'all'+'eg'+'e'='ALLEGE'
Can you help me to learn more?
(Other definitions for allege that I've seen before include "Make accusation without proof" , "Declare without actual proof" , "Assert, state without proof" , "hold" , "Declare without absolute proof" .)