This writer's past rendered in adult form (5)
I believe the answer is:
imago
'adult form' is the definition.
(adult form of an insect)
'this writer's past' is the wordplay.
'this writer's' becomes 'i'm' (referring to the person writing the clues).
'past' becomes 'ago' (similar in meaning).
'im'+'ago'='IMAGO'
'rendered in' acts as a link.
(Other definitions for imago that I've seen before include "Adult insect after metamorphosis" , "Post-pupa stage of an insect" , "That's as far as a butterfly can go" , "spinner, say" , "A mental picture" .)