Discard at tip (4)
I believe the answer is:
dump
I believe this is a double definition.
'discard' is the first definition.
(I know that dump is a more specific form of the action discard)
'tip' is the second definition.
(I know that tip can be written as dump)
'at' acts as a link.
(Other definitions for dump that I've seen before include "Dispose of" , "Disposal site" , "deposit" , "Public rubbish tip" , "waste ground?" .)