The end (5)
'the end' is the definition.
(the end of a life)
This is the entire clue.
(Other definitions for death that I've seen before include "Distribute; wood" , "The grim reaper" , "Annihilation" , "Last moment of existence" , ""The last enemy"" .)
(Other definitions for fin that I've seen before include "Swimmer" , "Piscine appendage" , "Fish propeller; end (Fr.)" , "Paddle-like organ" , "Swimmer's flipper" .)