Perhaps she lasted, being immortal (9)
I believe the answer is:
deathless
'being immortal' is the definition.
(similar in meaning)
'perhaps she lasted' is the wordplay.
'perhaps' indicates an anagram.
'she'+'lasted'='shelasted'
'shelasted' is an anagram of 'DEATHLESS'.
(Other definitions for deathless that I've seen before include "Lest heads, oddly, become everlasting" , "immortal" , "living forever" , "Never-ending" .)