Narrow passage without a spot in the sea (4)
I believe the answer is:
isle
'spot in the sea' is the definition.
(I've seen this in another clue)
'narrow passage without a' is the wordplay.
'narrow passage' becomes 'aisle' (I've seen this in another clue).
'without' is a deletion indicator.
'aisle' with 'a' removed is 'ISLE'.
(Other definitions for isle that I've seen before include "Body of land surrounded by water" , "Dogs, for example" , "The Emerald - (Ireland)" , "Piece of land in water" , "Small bit of land surrounded by water" .)