Smart guy with a counterfeit note (4)
I believe the answer is:
dude
'smart guy' is the definition.
'dude' can be an answer for 'guy' (both can informally mean a man). I'm unsure of the 'smart' bit.
'with a counterfeit note' is the wordplay.
'with' says to put letters next to each other.
'a counterfeit' becomes 'dud' (I've seen this before).
'note' becomes 'e' (musical note).
'dud' put next to 'e' is 'DUDE'.
Can you help me to learn more?
(Other definitions for dude that I've seen before include "Dandy - city dweller holidaying on ranch" , "A (dandy) American city dweller" , "Dandy - US or Canadian city dweller" , "Stylish chap" , "US geezer" .)