Feud almost over, tense time in London museum? (8)
I believe the answer is:
vendetta
'feud' is the definition.
(vendetta is a kind of feud)
I don't understand how the remainder of the clue works.
(Other definitions for vendetta that I've seen before include "A family feud in Sicily" , "A prolonged feud, associated with Sicily" , "Private feud" , "A prolonged feud of Sicilian origin" , "Long bitter row" .)