Meaner in rates adjustment (7)
I believe the answer is:
nastier
'meaner' is the definition.
('nasty' can be similar in meaning to 'mean')
'in rates adjustment' is the wordplay.
'adjustment' indicates an anagram.
'in'+'rates'='inrates'
'inrates' anagrammed gives 'NASTIER'.
(Other definitions for nastier that I've seen before include "Less pleasant" , "Less nice" , "more awkward" , "More horrid" , "More unpleasant or distasteful" .)