The concept of a man interrupting a politician (6)
I believe the answer is:
theory
'the concept' is the definition.
(theory is a kind of concept)
'a man interrupting a politician' is the wordplay.
'a man' becomes 'he' (he refers to a man).
'interrupting' indicates putting letters inside.
'a politician' becomes 'tory' (term for a Conservative Party politician).
'he' going within 'tory' is 'THEORY'.
'of' acts as a link.
(Other definitions for theory that I've seen before include "Abstract explanation" , "Idea to explain something, say evolution" , "Explanatory idea" , "Speculative view" , "Supposition, hypothesis" .)