Abandon narrow channel (5)
I believe the answer is:
ditch
I believe this clue is a double definition.
'abandon' is the first definition.
(ditching is a kind of abandoning)
'narrow channel' is the second definition.
(I've seen this before)
(Other definitions for ditch that I've seen before include "Dump (informal)" , "Type of trench" , "Abandon; one dug" , "Gully or furrow" , "Get rid of; dug channel" .)