Corrupt internet torrent partially backed up (6)
I believe the answer is:
rotten
'corrupt' is the definition.
(synonyms)
'internet torrent partially backed up' is the wordplay.
'partially' says the answer is hidden in the clue.
'backed up' shows that the letters should be reversed in order.
'nettor' can be found hidden inside 'internet torrent'.
'nettor' backwards is 'ROTTEN'.
(Other definitions for rotten that I've seen before include "Dedayed, stinking" , "Decayed, putrid" , "Lousy" , "'Gone bad, decayed (6)'" , "Informally, very much" .)