Reportedly recognises smell (4)
I believe the answer is:
nose
'smell' is the definition.
(nose is a kind of smell)
'reportedly recognises' is the wordplay.
'reportedly' shows a homophone (sound like).
'recognises' becomes 'knows' ('know' can be a synonym of 'recognize').
'knows' is a homophone of 'NOSE'.
(Other definitions for nose that I've seen before include "Faculty for detecting" , "In-your-face" , "Snout" , "Informer" , "scent" .)