Monsieur helps servants (5)
I believe the answer is:
maids
'servants' is the definition.
(maid is a kind of servant)
'monsieur helps' is the wordplay.
'monsieur' becomes 'm' (French abbreviation - like Mr for Mister).
'helps' becomes 'aids' ('aid' can be a synonym of 'help').
'm'+'aids'='MAIDS'
(Other definitions for maids that I've seen before include "Female domestic servants" , "Female domestics" , "Getting women in service" , "Lasses" , "girls!" .)