Regret violence ultimately following game (3)
I believe the answer is:
rue
'regret' is the definition.
(to rue something is to regret it)
'violence ultimately following game' is the wordplay.
'ultimately' suggests the final letters.
'following' is a charade indicator (letters next to each other).
'game' becomes 'ru' (rugby union).
The last letter of 'violence' is 'e'.
'e' put after 'ru' is 'RUE'.
(Other definitions for rue that I've seen before include "show regret" , "repentance" , "Regret; road (Fr.)" , "Bitterly regret - plant" , "Bitter-tasting herb" .)