Rubbish going up the hill (3)
I believe the answer is:
tor
'hill' is the definition.
(I know that tor is a type of hill)
'rubbish going up' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'going up' shows that the letters should be reversed in order (in a down clue, the letters are written upwards).
'rot' in reverse letter order is 'TOR'.
'the' is the link.
(Other definitions for tor that I've seen before include "Pillar of rock" , "Rot on a hill in Cornwall" , "rise" , "Rocky outcrop" , "Dartmoor peak" .)