Conservative leading committee is part of the furniture (8)
I believe the answer is:
cupboard
'is part of the furniture' is the definition.
(a furniture item might have a cupboard)
'conservative leading committee' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'leading' becomes 'up' (up can mean leading in a game).
'committee' becomes 'board' (board is a kind of committee).
'c'+'up'+'board'='CUPBOARD'
(Other definitions for cupboard that I've seen before include "Furniture item for storage" , "Closet" , "Piece of furniture used for storage" , "Press" , "Furniture for storing provisions etc." .)