Female also overturned base (4)
I believe the answer is:
foot
'base' is the definition.
('foot' can be a synonym of 'base')
'female also overturned' is the wordplay.
'female' becomes 'f' (abbreviation).
'also' becomes 'too' ('too' can be a synonym of 'also').
'overturned' says the letters should be written backwards.
'too' backwards is 'oot'.
'f'+'oot'='FOOT'
(Other definitions for foot that I've seen before include "Imperial distance" , "An imperial length or body part" , "Measure - part of body" , "See 24" , "Infantry - unit of linear measure" .)