Servants will give help in writing (5)
I believe the answer is:
maids
'servants' is the definition.
(maid is a kind of servant)
'help in writing' is the wordplay.
'help' becomes 'aid' ('aid' can be a synonym of 'help').
'in' means one lot of letters goes inside another.
'writing' becomes 'ms' (abbreviation for manuscript).
'aid' inserted inside 'ms' is 'MAIDS'.
'will give' acts as a link.
(Other definitions for maids that I've seen before include "Lasses" , "Getting women in service" , "Female domestics" , "Female domestic servants" , "girls!" .)