One who keeps a servant (8)
I believe the answer is:
retainer
'servant' is the definition.
(I know that servant can be written as retainer)
'one who keeps a' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'a' could be 'an' and 'an' is present in the remaining letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for retainer that I've seen before include "Eritrean as kind of servant" , "Old servant - fee paid in advance" , "Household servant (often faithful and old!)" , "given payment in advance" , "Eritrean (anag)" .)