Extra snake almost died (5)
I believe the answer is:
added
'extra' is the definition.
(something added is extra)
'snake almost died' is the wordplay.
'snake' becomes 'adder' (type of snake).
'almost' means to remove the last letter (almost the whole word is kept).
'died' becomes 'd' (abbreviation next to the year of someone's death).
'adder' with its last letter taken away is 'adde'.
'adde'+'d'='ADDED'
(Other definitions for added that I've seen before include "Summed up" , "Totted" , "Said" , "Contributed" , "Extra" .)