Ambassador blocks Conservative plan (6)
I believe the answer is:
theory
'plan' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Maybe there's a link between them I don't understand?
'ambassador blocks conservative' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'blocks' means one lot of letters goes inside another (upper walls off glass inside formal).
'conservative' becomes 'tory' (informal term for a Conservative Party member).
'he' inserted inside 'tory' is 'THEORY'.
Can you help me to learn more?
(Other definitions for theory that I've seen before include "Proposed explanation of something" , "Speculation" , "Conjectural view" , "Conjecture, hypothesis" , "Set of ideas formulated to explain something" .)