Eternally young boy’s potential energy initially worried parent (5,3)
I believe the answer is:
peter pan
'eternally young boy's potential' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'energy initially worried parent' is the wordplay.
'energy' becomes 'pe' (P.E. is an example).
'initially' is a charade indicator (letters next to each other) (some letters go before others).
'worried' indicates an anagram (worry can mean to interfere with or disturb).
'parent' with letters rearranged gives 'terpan'.
'pe'+'terpan'='PETER PAN'
Can you help me to learn more?
(Other definitions for peter pan that I've seen before include "Barrie's ageless youth" , "Ever-youthful boy" , "Pantomime hero" , "JM Barrie character" , "Boyish creation of J.M. Barrie" .)