Lad that is treated right may become perfect (5)
I believe the answer is:
ideal
'perfect' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for ideal that I've seen before include "Perfect for the purpose" , "An - - Husband (Wilde)" , "fanciful" , "In her dreams" , "Most suitable" .)