Room for a bullet perhaps (7)
I believe the answer is:
chamber
'room' is the definition.
(chamber is a kind of room)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for chamber that I've seen before include "Judge's room" , "Large room" , "A formal room as for judge" , "Judicial assembly - room" , "Official room" .)