Isle of Man, once? (5)
I believe the answer is:
wight
I believe this is a double definition.
'isle' is the first definition.
(Isle of Wight)
'man once?' is the second definition.
(archaic term for a person)
'of' is the link.
(Other definitions for wight that I've seen before include "An Isle; a man (obs.)" , "Spirit, ghost" , "reproach" , "Isle - sea area" , "Solent island" .)