Man, maybe, in passageway, losing head (4)
I believe the answer is:
isle
'man maybe' is the definition.
(Isle of Man)
'passageway losing head' is the wordplay.
'passageway' becomes 'aisle' (aisle is a kind of passageway).
'losing head' means to remove the first letter.
'aisle' with its initial letter removed is 'ISLE'.
'in' acts as a link.
(Other definitions for isle that I've seen before include "Geographic location" , "Small island" , "Small landmass" , "description of Britain" , "Rum, for example" .)