Positive aspect is due to reform, quietly included (6)
I believe the answer is:
upside
'positive aspect' is the definition.
(I've seen this in another clue)
'is due to reform quietly included' is the wordplay.
'to reform' indicates an anagram (letters in a new form).
'quietly' becomes 'p' (p for piano and quiet).
'included' indicates putting letters inside.
'is'+'due'='isdue'
'isdue' with letters rearranged gives 'uside'.
'uside' going around 'p' is 'UPSIDE'.
(Other definitions for upside that I've seen before include "Positive aspect of a situation" , "Favourable aspect" , "Top surface of something" , "advantage" .)