Feud: old soldier cheers, welcoming conclusion (8)
I believe the answer is:
vendetta
'feud' is the definition.
(vendetta is a kind of feud)
'old soldier cheers welcoming conclusion' is the wordplay.
'old soldier' becomes 'vet' (veteran).
'cheers' becomes 'ta' (both can mean thank you).
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'conclusion' becomes 'end' (something's conclusion is its end).
'vet'+'ta'='vetta'
'vetta' placed around 'end' is 'VENDETTA'.
(Other definitions for vendetta that I've seen before include "Bitter feud between families" , "A prolonged feud of Sicilian origin" , "A family feud in Sicily" , "Unremitting battle" , "Murderous feud" .)