Fireplace large, we hear (5)
I believe the answer is:
grate
'fireplace' is the definition.
(grate can mean a fireplace)
'large we hear' is the wordplay.
'large' becomes 'great' (synonyms).
'we hear' shows a homophone (sound like).
'great' is a homophone of 'GRATE'.
(Other definitions for grate that I've seen before include "Fireplace recess; rasp" , "Shred; scrape" , "Grind (cheese)" , "Make a harsh rasping sound" , "irritating" .)