Had been a forger, one didn't let oneself forget (4,1,4)

'forger one didn't let oneself forget' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'had been a' is the wordplay.
I cannot quite understand how this works, but
'had' could be 'made' ('make' can be a synonym of 'have') and 'made' is located in the answer.
'a' could be 'an' and 'an' is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?