Don't talk about fate or sin (5)
I believe the answer is:
sloth
'sin' is the definition.
(sloth is a kind of sin)
'don't talk about fate' is the wordplay.
'don't talk' becomes 'sh' (I've seen this in other clues).
'about' means one lot of letters goes inside another.
'fate' becomes 'lot' (synonyms).
'sh' placed around 'lot' is 'SLOTH'.
'or' is the link.
(Other definitions for sloth that I've seen before include "Torpor" , "Arboreal creature" , "Jungle mammal; laziness" , "one of a deadly group" , "One's often suspended from tree" .)