Female at the time needing to lose weight (3)
I believe the answer is:
hen
'female' is the definition.
(hen is a kind of female)
'the time needing to lose weight' is the wordplay.
'the time' becomes 'when' (I've seen this before).
'needing to lose' indicates named letters should be taken away.
'weight' becomes 'w'.
'when' with 'w' taken away is 'HEN'.
'at' is the link.
(Other definitions for hen that I've seen before include "Source of eggs" , "Female lobster, fowl" , "Domestic fowl" , "Farm bird" , "Laying bird" .)