Visitor reckoned to be heard (5)
I believe the answer is:
guest
'visitor' is the definition.
(guest is a kind of visitor)
'reckoned to be heard' is the wordplay.
'reckoned' becomes 'guessed' (guessing is a kind of reckoning).
'to be heard' shows a homophone (sound like).
'guessed' sounds like 'GUEST'.
(Other definitions for guest that I've seen before include "Visitant" , "Hotel resident" , "Visitor to whom hospitality is extended" , "Invited visitor" , "Invited person" .)