Phony coin (4)
I believe the answer is:
slug
'phony coin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slug that I've seen before include "Bullet; swig" , "Slimy gastropod" , "Heavy blow for snail lacking shell" , "Projectile fired from a gun" , "Bullet - punch" .)