Remains quiet after answer (3)
I believe the answer is:
ash
'remains' is the definition.
(remains of a fire)
'quiet after answer' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'after' means one lot of letters go next to another.
'answer' becomes 'a' (abbreviation eg in Q and A).
'sh' after 'a' is 'ASH'.
(Other definitions for ash that I've seen before include "Burnt material; tree" , "In fireplace it may be" , "It no longer burns" , "Part of forest" , "Grey colour" .)