Boy's name for a Hampstead "wood" (3)
I believe the answer is:
ken
'boy's' is the definition.
(man's name)
'name for a hampstead wood' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'for' says to put letters next to each other (I've seen this in other clues).
'a hampstead wood' becomes 'ke' (I can't justify this - if you can you should give a lot more credence to this answer).
'n' after 'ke' is 'KEN'.
Can you help me to learn more?
(Other definitions for ken that I've seen before include "Understanding - boy's name" , "Know; man's name" , "One's range of knowledge" , "Notice" , "Awareness" .)