He stops Tory speculation (6)
I believe the answer is:
theory
'speculation' is the definition.
(something theorised or speculated)
'he stops tory' is the wordplay.
'stops' indicates putting letters inside (stopping can mean blocking a gap).
'he' going into 'tory' is 'THEORY'.
(Other definitions for theory that I've seen before include "Conjectural view" , "A conjecture to explain something" , "Set of principles on which practice is based" , "Supposition intended to explain observations" , "Opinion or supposition to explain something" .)