They keep servants (9)
I believe the answer is:
retainers
'servants' is the definition.
('retainer' can be a synonym of 'servant')
'they keep' is the wordplay.
I cannot quite see how this works, but
'keep' could be 'retain' (retaining is a kind of keeping) and 'retain' is found in the answer.
The remaining letters 'ers' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for retainers that I've seen before include "Family servants" , "Financial inducements" , "Money deposits or servants to nobility" .)