Claim a £50 note at some stage (6)
I believe the answer is:
allege
'claim' is the definition.
(to allege something is to make a claim)
'a ps50 note at some stage' is the wordplay.
'a ps50' becomes 'al' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'note' becomes 'e' (musical note).
'at' means one lot of letters go next to another (I've seen this in other clues).
'some stage' becomes 'leg' (a leg is a stage of a competition).
'e' after 'leg' is 'lege'.
'al'+'lege'='ALLEGE'
Can you help me to learn more?
(Other definitions for allege that I've seen before include "Aver (without proof)" , "Declare without absolute proof" , "Declare without actual proof" , "Assert - maintain" , "Declare without being able to prove" .)