Spirits supplied by good landlords (6)
'spirits' is the definition.
(ghost is a kind of spirit)
'good landlords' is the wordplay.
'good' becomes 'g' (abbreviation).
'landlords' becomes 'hosts' (I've seen this before).
'supplied by' is the link.
(Other definitions for ghosts that I've seen before include "Spectres, wraiths", "Spooks, spectres", "Writes for another; Ibsen play", "Apparitions of a dead people", "Spirits or apparitions".)