Sin among men vying (4)
I believe the answer is:
envy
'sin' is the definition.
(I know that envy is a type of deadly sin)
'among men vying' is the wordplay.
'among' indicates the answer is hidden within the clue.
'ENVY' is hidden in the letters of 'men vying'.
(Other definitions for envy that I've seen before include "Wish for thing or quality belonging to another" , "Desire of another's property etc" , "Begrudge, covet" , "One of 7 vices" , "Bad feeling" .)