Man having many a slave (5)
I believe the answer is:
helot
'a slave' is the definition.
(I've seen this before)
'man having many' is the wordplay.
'man' becomes 'he' (**).
'having' means one lot of letters go next to another.
'many' becomes 'lot' (I've seen this before).
'he'+'lot'='HELOT'
(Other definitions for helot that I've seen before include "Serf of ancient Sparta" , "Hotel (anag) - serf" , "Greek serf" , "He's bound to land" , "One made to work" .)