Promotion of MP with rent-free accommodation (10)
I believe the answer is:
preferment
'promotion' is the definition.
(preferment is a kind of promotion)
'mp with rent-free accommodation' is the wordplay.
'with' means one lot of letters go next to another.
'accommodation' indicates an anagram.
'rent'+'free'='rentfree'
'mp' put after 'rentfree' is 'rentfreemp'.
'rentfreemp' is an anagram of 'PREFERMENT'.
'of' is the link.
(Other definitions for preferment that I've seen before include "step ahead?" , "Promotion to higher office" .)