Sin of a group of lions? (5)
I believe the answer is:
pride
This clue is a double definition.
'sin' is the first definition.
(pride is a kind of sin)
'group of lions?' is the second definition.
(I've seen this before)
'of a' acts as a link.
(Other definitions for pride that I've seen before include "Group of lions" , "Arrogance - self-respect" , "Vanity" , "group of animals" , "Company of lions" .)