Support son, overweight, knocked back by female (5)
I believe the answer is:
staff
'support' is the definition.
(thesaurus)
'son overweight knocked back by female' is the wordplay.
'son' becomes 's'.
'overweight' becomes 'fat' (I've seen this before).
'knocked back' says the letters should be written in reverse.
'by' says to put letters next to each other.
'female' becomes 'f' (abbreviation).
'fat' in reverse letter order is 'taf'.
's'+'taf'+'f'='STAFF'
(Other definitions for staff that I've seen before include "men?" , "See 11" , "Take a rod to the personnel?" , "Emblem of authority" , "Rod - workforce" .)