Female to sicken and disappoint (4)
I believe the answer is:
fail
'disappoint' is the definition.
(I know that fail is a more specific form of disappoint)
'female to sicken' is the wordplay.
'female' becomes 'f' (abbreviation).
'to sicken' becomes 'ail' (I've seen this before).
'f'+'ail'='FAIL'
'and' acts as a link.
(Other definitions for fail that I've seen before include "Come to naught" , "Go wrong" , "Fall short" , "Run out; flop" , "Neglect (to do something)" .)