Falls short of a pound note - counterfeit perhaps (5)
I believe the answer is:
'counterfeit perhaps' is the definition.
'false' can be an answer for 'counterfeit' (I've seen this in another clue). I'm not certain of the 'perhaps' bit.
'falls short of a pound note' is the wordplay.
'short of' is a deletion indicator.
'a pound' becomes 'L' (the pound sign is based on an L).
'note' becomes 'e' (musical note).
'falls' with 'l' taken out is 'fals'.
Can you help me to learn more?
(Other definitions for false that I've seen before include "Not in accordance with fact" , "Invalid; untrue" , "Spurious, untrue" , "Wrong" , "Incorrect" .)