Confuses or goes bad (6)
I believe the answer is:
addles
I believe this is a double definition.
'confuses' is the first definition.
(addling is a kind of confusing)
'goes bad' is the second definition.
(addling is a kind of going bad)
(Other definitions for addles that I've seen before include "Confuses, befuddles" , "Muddles, confuses" , "Confuses in saddle" , "Makes rotten - makes muddled" , "Confuses or becomes rotten" .)