Don't talk about fate and sin (5)
I believe the answer is:
sloth
'sin' is the definition.
(I know that sloth is a sin)
'don't talk about fate' is the wordplay.
'don't talk' becomes 'sh' ('sh' is used to tell someone to be quiet).
'about' is an insertion indicator.
'fate' becomes 'lot' (synonyms).
'sh' going around 'lot' is 'SLOTH'.
'and' is the link.
(Other definitions for sloth that I've seen before include "Laziness; slow mammal" , "Arboreal creature" , "Indolence" , "Arboreal animal" , "One hangs a lot" .)