Pleased with good boy (4)
I believe the answer is:
glad
'pleased with' is the definition.
(thesaurus)
'good boy' is the wordplay.
'good' becomes 'g' (abbreviation).
'boy' becomes 'lad' (lad is a kind of boy).
'g'+'lad'='GLAD'
(Other definitions for glad that I've seen before include "More than willing" , "Joyful" , "Made up" , "Happy, pleased" , "Elated" .)