Vacant English politician is extreme Tory (5)
I believe the answer is:
empty
'vacant' is the definition.
(similar in meaning)
'english politician is extreme tory' is the wordplay.
'english' becomes 'E' (abbreviation as in OED).
'politician' becomes 'MP' (Member of Parliament).
'is extreme' says to hollow out the word (remove centre letters).
'tory' with its middle removed is 'ty'.
'e'+'mp'+'ty'='EMPTY'
(Other definitions for empty that I've seen before include "Hollow or vacant" , "Like the sherry decanter by the time gran's jolly" , "Drained glass" , "Cleared out" , "Devoid of content" .)