In tandem arranged fair adaptation (10)
I believe the answer is:
adjustment
'adaptation' is the definition.
(I know that adaptation can be written as adjustment)
'in tandem arranged fair' is the wordplay.
'in' indicates putting letters inside.
'arranged' indicates an anagram.
'fair' becomes 'just' (synonyms).
'tandem' is an anagram of 'adment'.
'adment' going around 'just' is 'ADJUSTMENT'.
(Other definitions for adjustment that I've seen before include "Adaptation" , "Minor modification" , "Modification; regulation" , "Ordering" , "Fitting" .)