Females desirable, formerly, in certain places (7)

I believe the answer is:

sexpots

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'females desirable' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'formerly in certain places' is the wordplay.
'formerly' becomes 'ex' (prefix meaning former or onetime).
'in' means one lot of letters goes inside another.
'certain places' becomes 'spots' ('spot' can be a synonym of 'place'. I am not sure about the 'certain' bit.).
'ex' placed inside 'spots' is 'SEXPOTS'.

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I've seen this clue in the Evening Standard.

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