Person entertained in the vaguest sense (5)
I believe the answer is:
guest
'person entertained' is the definition.
(I've seen this before)
'in the vaguest sense' is the wordplay.
'in' says the answer is hidden in the clue.
'GUEST' is hidden in the letters of 'vaguest sense'.
(Other definitions for guest that I've seen before include "One who's invited" , "company" , "Visitor, lodger" , "Person entertained by host" , "Invited person" .)