Visitor supposed to speak (5)
I believe the answer is:
guest
'visitor' is the definition.
(guest is a kind of visitor)
'supposed to speak' is the wordplay.
'supposed' becomes 'guessed' ('guess' can be a synonym of 'suppose').
'to speak' shows a homophone (sound like).
'guessed' is a homophone of 'GUEST'.
(Other definitions for guest that I've seen before include "One receiving hospitality" , "Conjectured audibly" , "Someone invited" , "Person receiving another's hospitality" , "Visitor to whom hospitality is extended" .)