Rubbish almost torn up (3)
I believe the answer is:
rot
'rubbish' is the definition.
(both can mean nonsense)
'almost torn up' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'up' is a reversal indicator (in down clue: letters go upwards).
'torn' with its final letter removed is 'tor'.
'tor' backwards is 'ROT'.
(Other definitions for rot that I've seen before include "Rhubarb" , "Corruption" , "Cobblers" , "Deteriorate" , "Putrefy" .)