Dread blunder by Tory leader (6)
I believe the answer is:
terror
'dread' is the definition.
(thesaurus)
'blunder by tory leader' is the wordplay.
'blunder' becomes 'error' (I've seen this before).
'by' says to put letters next to each other.
'tory leader' becomes 't' (I've seen this in other clues).
'error' after 't' is 'TERROR'.
(Other definitions for terror that I've seen before include "Panicky fright" , "Overwhelming feeling of fear" , "Young rascal -- horror" , "Organised political violence" , "State of extreme fright" .)