Good young fellow, and contented (4)
I believe the answer is:
glad
'contented' is the definition.
(I've seen this in another clue)
'good young fellow' is the wordplay.
'good' becomes 'g' (abbreviation).
'young fellow' becomes 'lad' (lad can mean a young boy).
'g'+'lad'='GLAD'
'and' acts as a link.
(Other definitions for glad that I've seen before include "happiness" , "More than willing" , "Little flowering plant" , "Not sorry" , "Feeling happy" .)