Channel or trench (5)
I believe the answer is:
ditch
I believe this is a double definition.
'channel' is the first definition.
(a small channel or trench in the ground)
'trench' is the second definition.
(synonyms)
'or' is the link.
(Other definitions for ditch that I've seen before include "Dump (informal)" , "Scrap" , "Boundary trench" , "Excavated channel" , "Type of trench" .)