Crossword Genius

Last month, when the accounts should have been settled (7)

Ross

I believe the answer is:

yearend

I'm a little stuck... Click here to teach me more about this clue!

'month when the accounts should have been settled' is the definition.
I know nothing about this answer so I can't tell whether this works.

'last' is the wordplay.
I cannot really see how this works, but
'last' could be 'end' (I've seen this in another clue) and 'end' is located in the answer.
The remaining letters 'year' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Irish Times.
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