Familiar name for humble member of a large organisation (women only) (8)
I believe the answer is:
cognomen
'familiar name' is the definition.
(type of ancient Roman name)
'humble member of a large organisation women only' is the wordplay.
'humble member of a large organisation' becomes 'cog' (a cog in the machine).
'women only' becomes 'no men' (only women - no men).
'cog'+'nomen'='COGNOMEN'
'for' is the link.
(Other definitions for cognomen that I've seen before include "Con gnome using kind of nickname" , "Nickname -- eg non-com (anag)" , "Family name" , "Epithet" .)