Be patronising towards women denied sons (5)
I believe the answer is:
exist
'be' is the definition.
(synonyms)
'patronising towards women denied sons' is the wordplay.
'patronising towards women' becomes 'sexist'.
'denied' is a deletion indicator (the word is denied or deprived of some letters).
'sons' becomes 's'.
'sexist' with 's' taken away is 'EXIST'.
(Other definitions for exist that I've seen before include "Have objective reality" , "Subsist" , "quick!" , "Be alive" , "Have being or continue living" .)