Finish immersed in splendour (3)
I believe the answer is:
end
'finish' is the definition.
(come to an end)
'immersed in splendour' is the wordplay.
'immersed in' indicates the answer is hidden within the clue.
'END' is hidden within 'splendour'.
(Other definitions for end that I've seen before include "Finish; goal" , "Finish, close" , "border?" , "Complete" , "'Conclusion, finale (3)'" .)