When one was poor and didn't have to slim? (4,5)

'when one was poor' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'didn't have to slim?' is the wordplay.
'didn't have' becomes 'years' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'slim?' becomes 'lean' (similar in meaning).
'years' after 'lean' is 'LEAN YEARS'.

'and' acts as a link.

Can you help me to learn more?