Stablemen at inns of old (7)
I believe the answer is:
ostlers
'stablemen at inns of old' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ostlers that I've seen before include "They used to stable horses at inns" , "Let Ross join in group of old stable managers" , "They looked after the horses at the inns of old" , "Historically they looked after the horses at an inn" , "Stablemen at inns of old" .)