Narrow channel (5)
'narrow channel' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ditch that I've seen before include "Excavated channel" , "drainage feature" , "Boundary trench" , "Abandon - trench" , "Moat" .)
'narrow channel' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for strait that I've seen before include "Catch in a trap" , "Hardship - narrow passage of water" , "Narrow watery stretch" , "Connecting passage of water" , "Narrow passage joining two large areas of water" .)