Sod’s green after treatment is absorbed (9)
I believe the answer is:
engrossed
'is absorbed' is the definition.
('engrossed' can be a synonym of 'absorbed')
'sod's green after treatment' is the wordplay.
'after treatment' is an anagram indicator.
'sods'+'green'='sodsgreen'
'sodsgreen' anagrammed gives 'ENGROSSED'.
(Other definitions for engrossed that I've seen before include "Completely absorbed, rapt" , "Totally absorbed" , "Captive" , "Consumed" , "Gripped" .)