Knave taking half of room and half of guests (5)
I believe the answer is:
rogue
'knave' is the definition.
(I know that knave can be written as rogue)
'half of room and half of guests' is the wordplay.
'half of' means to take half the letters.
'and' is a charade indicator (letters next to each other).
'half of' suggests halving the letters.
'room' with half the letters taken is 'ro'.
'guests' cut in half is 'gue'.
'ro'+'gue'='ROGUE'
'taking' acts as a link.
(Other definitions for rogue that I've seen before include "Wild animal driven away from herd" , "Baddie" , "Scamp" , "Miscreant" , "Unprincipled man" .)