Suppressing anger is far more dispassionate (6)
I believe the answer is:
fairer
'more dispassionate' is the definition.
('fair' can be similar in meaning to 'dispassionate')
'suppressing anger is far' is the wordplay.
'suppressing' indicates putting letters inside.
'anger' becomes 'ire' (ire is intense rage).
'ire' placed into 'far' is 'FAIRER'.
(Other definitions for fairer that I've seen before include "More equitable or blonde" , "More reasonable" , "lighter" , "Cleaner" , "Blonder" .)