Female prisoner to tire (4)

I believe the answer is:

flag

'to tire' is the definition.
(I've seen this in another clue)

'female prisoner' is the wordplay.
'female' becomes 'f' (common abbreviation).
'prisoner' becomes 'lag' (slang term).
'f'+'lag'='FLAG'

(Other definitions for flag that I've seen before include "sink" , "Colours a paving stone" , "Iris; pennant" , "what Amundsen planted" , "Draw attention to" .)

I've seen this clue in The Times.

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