Charge to invest a couple of thousand for a woman (5)

'a woman' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

'charge to invest a couple of thousand' is the wordplay.
'charge' becomes 'fee' (fee is a kind of charge).
'to invest' means one lot of letters goes inside another.
'a couple of' indicates the doubling of some letters.
'thousand' becomes 'm' (Roman numeral for a thousand).
'm' doubled is 'mm'.
'fee' going around 'mm' is 'FEMME'.

'for' acts as a link.

Can you help me to learn more?