Tale of one's past or youth (5)
I believe the answer is:
story
'tale' is the definition.
(synonyms)
'of one's past or youth' is the wordplay.
'of' says the answer is hidden in the clue.
'STORY' is hidden within 'ones past or youth'.
(Other definitions for story that I've seen before include "Tale - lie" , "Narration" , "See 10 and 19" , "Rumour" , "Anecdote" .)