Be biased against women perhaps not having sons (5)
I believe the answer is:
exist
'be' is the definition.
('exist' can be a synonym of 'be')
'biased against women perhaps not having sons' is the wordplay.
'biased against women perhaps' becomes 'sexist'.
'not having' is a deletion indicator.
'sons' becomes 's'.
'sexist' with 's' taken away is 'EXIST'.
(Other definitions for exist that I've seen before include "Have objective reality" , "Subsist" , "Survive" , "Live" , "Have being or continue living" .)