Room for experimentation in party rhetoric (10)
I believe the answer is:
laboratory
'room for experimentation' is the definition.
'party rhetoric' is the wordplay.
'party' becomes 'lab' (abbreviation for Labour).
'rhetoric' becomes 'oratory' (both can mean formal speech).
'lab'+'oratory'='LABORATORY'
'in' is the link.
(Other definitions for laboratory that I've seen before include "Where researchers work" , "Language-learning facility" , "workplace" , "Where one investigates" , "Place of scientific research" .)