Wretched old Tory right-wingers holding back (6)
I believe the answer is:
dreary
'wretched' is the definition.
(thesaurus)
'old tory right-wingers holding back' is the wordplay.
'right-wingers' suggests the final letters (the rightmost letter in the word).
'holding' is an insertion indicator.
'back' becomes 'rear' ('rear' can be a synonym of 'back'**).
The final letters of 'old tory' are 'dy'.
'dy' enclosing 'rear' is 'DREARY'.
(Other definitions for dreary that I've seen before include "Depressingly dull" , "Gloomy - dull" , "Bleak, depressing" , "Dull and depressing" , "Dark" .)