Female just horrible (9)
I believe the answer is:
frightful
'horrible' is the definition.
('frightful' can be a synonym of 'horrible')
'female just' is the wordplay.
'female' becomes 'f' (abbreviation).
'just' becomes 'rightful' ('rightful' can be similar in meaning to 'just').
'f'+'rightful'='FRIGHTFUL'
(Other definitions for frightful that I've seen before include "nasty" , "ugly" , "Terrible, awful" , "very bad" , "horrible" .)