What's up with Conservative housing proposition? (6)
I believe the answer is:
theory
'proposition?' is the definition.
(both can mean an idea or hypothesis)
'what's up with conservative housing' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'up' is a reversal indicator (in down clue: letters go upwards).
'with conservative' becomes 'tory' (Tory means a member of the Conservative Party. I am not sure about the 'with' bit.).
'housing' indicates putting letters inside.
'eh' reversed gives 'he'.
'he' placed into 'tory' is 'THEORY'.
Can you help me to learn more?
(Other definitions for theory that I've seen before include "Supposition or idea" , "(Scientific) explanation" , "Conjectural view" , "Explanation or system of anything" , "Explanatory idea" .)