Pampered son accumulated entertaining dross essentially (7)
I believe the answer is:
spoiled
'pampered' is the definition.
('spoil' can be a synonym of 'pamper')
'son accumulated entertaining dross essentially' is the wordplay.
'son' becomes 's'.
'accumulated' becomes 'piled' (I can't justify this - if you can you should give a lot more credence to this answer).
'entertaining' is an insertion indicator.
'essentially' says to take the centre.
The middle letter of 'dross' is 'o'.
'piled' going around 'o' is 'poiled'.
's'+'poiled'='SPOILED'
Can you help me to learn more?
(Other definitions for spoiled that I've seen before include "Of child, excessively pampered" , "Marred" , "Rotten" , "Damaged, harmed" , "Ruined" .)