Irish forged coin makes you rich (6)
I believe the answer is:
ironic
'rich' is the definition.
(I've seen this before)
'irish forged coin' is the wordplay.
'irish' becomes 'IR' (abbreviation).
'forged' indicates an anagram.
'coin' is an anagram of 'onic'.
'ir'+'onic'='IRONIC'
'makes you' acts as a link.
(Other definitions for ironic that I've seen before include "Wryly humorous" , "Meaning the contrary of what is expressed" , "A form of sarcasm, may sound perverse" , "not as you'd expect" , "likely to provoke a wry smile" .)