The pawnbroker may find a hundred pounds in a French one (5)
I believe the answer is:
uncle
'the pawnbroker' is the definition.
(old-fashioned term for a pawnbroker)
'a hundred pounds in a french one' is the wordplay.
'a hundred' becomes 'C' (Roman numerals).
'pounds' becomes 'l' (abbreviation e.g. Lsd - pounds, shillings, pence).
'in' indicates putting letters inside.
'a french one' becomes 'une' (I've seen this in another clue).
'c'+'l'='cl'
'cl' going inside 'une' is 'UNCLE'.
'may find' acts as a link.
(Other definitions for uncle that I've seen before include "One receiving pawn" , "Male family member" , "Dad's brother" , "Brother of one's parent" , "Pawnbroker (sl.)" .)