Supervisor continued to get posh car (10)
I believe the answer is:
controller
'supervisor' is the definition.
(thesaurus)
'continued to get posh car' is the wordplay.
'continued' becomes 'cont' (common abbreviation).
'to get' is a charade indicator (letters next to each other).
'posh car' becomes 'roller' (informal term for Rolls Royce).
'cont'+'roller'='CONTROLLER'
(Other definitions for controller that I've seen before include "Regulator" , "One holding the reins" .)