Young male tot having rest outside (6)
I believe the answer is:
laddie
'young male' is the definition.
'tot having rest outside' is the wordplay.
'tot' becomes 'add' ('add' can be a synonym of 'tot').
'having rest' becomes 'lie' (I can't explain this - if you can you should give a lot more credence to this answer).
'outside' is an insertion indicator.
'add' put within 'lie' is 'LADDIE'.
Can you help me to learn more?
(Other definitions for laddie that I've seen before include "Youngster" , "Scottish boy" , "(Scots) boy" , "Sonny" , "Child" .)