Youngster apt to bite? (6)
I believe the answer is:
nipper
'youngster' is the definition.
(I know that nipper is a type of youngster)
'apt to bite?' is the wordplay.
'apt' becomes 'per' (I can't justify this - if you can you should believe this answer much more).
'to' says to put letters next to each other (I've seen this in other clues).
'bite?' becomes 'nip' (nipping is a kind of biting).
'per' put after 'nip' is 'NIPPER'.
Can you help me to learn more?
(Other definitions for nipper that I've seen before include "Child (informal); one biting" , "Infant (colloq.)" , "Child (slang); one that 19s" , "Crab - young shaver?" , "Child - ankle-biter?" .)