Hail in a part of Orkney (4)
I believe the answer is:
ahoy
'hail' is the definition.
(I've seen this before)
'a part of orkney' is the wordplay.
'part of orkney' becomes 'Hoy' (island in Orkney, Scotland).
'a'+'hoy'='AHOY'
'in' is the link.
(Other definitions for ahoy that I've seen before include "Nautical greeting" , "Sailor's greeting" , "Hail at sea" , "Sailor's cry to ship" , "(Nautical) hailing call" .)