A stayer, shall we say? (5)
I believe the answer is:
guest
'say?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for guest that I've seen before include "Visitor to whom hospitality is extended" , "One who's invited" , "Caller" , "Person entertained by host" , "who takes hotel room" .)