Falls short of a pound note - counterfeit perhaps (5)
I believe the answer is:
false
'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'.
'fals'+'e'='FALSE'
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" .)