The plane crash one never forgets (8)
I believe the answer is:
elephant
'one never forgets' is the definition.
(supposedly, elephants never forget)
'the plane crash' is the wordplay.
'crash' indicates an anagram.
'the'+'plane'='theplane'
'theplane' is an anagram of 'ELEPHANT'.
(Other definitions for elephant that I've seen before include "bigger one from two continents?" , "Large animal found in the plane?" , "Trunk carrier?" , "Trunked mammal" , "Tusked mammal" .)