Do what certain people don't, but do reform (5)
I believe the answer is:
doubt
'do what certain people don't' is the definition.
I can't tell whether this defines the answer.
'but do reform' is the wordplay.
'reform' indicates an anagram (letters in a new form).
'but'+'do'='butdo'
'butdo' is an anagram of 'DOUBT'.
Can you help me to learn more?
(Other definitions for doubt that I've seen before include "Uncertainty, unsureness" , "Question the truth or accuracy of" , "Suspicion" , "Feel uncertain about" , "Uncertainty about the truth" .)