Copper's revolutionary cab stolen (9)
I believe the answer is:
constable
'copper's' is the definition.
(thesaurus)
'revolutionary cab stolen' is the wordplay.
'revolutionary' indicates an anagram.
'cab'+'stolen'='cabstolen'
'cabstolen' anagrammed gives 'CONSTABLE'.
(Other definitions for constable that I've seen before include "CARRY ON FILM" , "Flatford Mill painter" , "In England, a great painter or lowly policeman" , "PC" , "the governor of a royal castle" .)