More dismal raise that is accepted by doctor (8)
I believe the answer is:
drearier
'more dismal' is the definition.
'raise that is accepted by doctor' is the wordplay.
'raise' becomes 'rear' ('rear' can be a synonym of 'raise'**).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'accepted by' means one lot of letters goes inside another.
'doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor').
'rear'+'ie'='rearie'
'rearie' placed into 'dr' is 'DREARIER'.
(Other definitions for drearier that I've seen before include "More dismal and gloomy" , "More tedious" , "More cheerless and dull" , "Not so exciting" .)