See groups backing Conservative in small rooms (7)
I believe the answer is:
closets
'small rooms' is the definition.
(closet can mean a small room)
'see groups backing conservative' is the wordplay.
'see' becomes 'lo' (archaic word meaning 'look!').
'groups' becomes 'sets' (I've seen this in other clues).
'backing' means one lot of letters go next to another.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'lo'+'sets'='losets'
'losets' put after 'c' is 'CLOSETS'.
'in' acts as a link.
(Other definitions for closets that I've seen before include "Hides away" , "American wardrobes" .)