Apparition revealed by good entertainer (5)
I believe the answer is:
ghost
'apparition' is the definition.
(ghost is a kind of apparition)
'by good entertainer' is the wordplay.
'by' says to put letters next to each other.
'good' becomes 'g' (abbreviation).
'entertainer' becomes 'host' (person hosting or entertaining guests).
'g' next to 'host' is 'GHOST'.
'revealed' is the link.
(Other definitions for ghost that I've seen before include "Write for another" , "Spectre, wraith" , "author for someone" , "Supernatural apparition" , "Visible manifestation of a dead person" .)