Discard in tip (4)
I believe the answer is:
dump
This clue is a double definition.
'discard' is the first definition.
(I know that dump is a type of discard)
'tip' is the second definition.
(I know that tip can be written as dump)
'in' is the link.
(Other definitions for dump that I've seen before include "Get rid of" , "Rubbishy place" , "Place where rubbish is deposited" , "Unload" , "Offload" .)