Bounds, more cocky, embracing yours truly's sweetheart (9)
I believe the answer is:
perimeter
'bounds' is the definition.
(thesaurus)
'more cocky embracing yours truly's sweetheart' is the wordplay.
'more cocky' becomes 'perter' (I can't justify this - if you can you should give a lot more credence to this answer).
'embracing' means one lot of letters goes inside another.
'yours truly's' becomes 'im' (I'm).
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'im'+'e'='ime'
'perter' placed around 'ime' is 'PERIMETER'.
Can you help me to learn more?
(Other definitions for perimeter that I've seen before include "Prime tree (anag.)" , "bounds" , "limits" , "Border" , "Bound" .)