First person is only human, though they may seem indestructible (8)
I believe the answer is:
immortal
'indestructible' is the definition.
(thesaurus)
'first person is only human though they may seem' is the wordplay.
I cannot really see how this works, but
'first' could be 'i' (I in Roman numerals eg Elizabeth I) and 'i' is found in the answer.
'person' could be 'mortal' (synonyms) and 'mortal' is found in the answer.
A single letter 'm' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for immortal that I've seen before include "Living for ever" , "Undying" , "God" , "Everlasting" , "Enduring" .)