Socialist has hospital department leased (6)
I believe the answer is:
rented
'leased' is the definition.
('rent' can be a synonym of 'lease')
'socialist has hospital department' is the wordplay.
'socialist' becomes 'red' (red can informally mean a socialist).
'has' is an insertion indicator.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'red' going around 'ent' is 'RENTED'.
(Other definitions for rented that I've seen before include "Hired - tender (anag)" , "Taken for hire" , "Leased" , "Let for money" .)