Dig this, or discard unceremoniously (5)
I believe the answer is:
ditch
'dig' is the definition.
(ditching is a kind of digging)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ditch that I've seen before include "Get rid of; dug channel" , "Narrow channel" , "Boundary trench" , "Drainage trench" , "Excavated channel" .)