Biased? Badly so, indeed (3-5)
I believe the answer is:
one-sided
'biased?' is the definition.
('one-sided' can be a synonym of 'biased')
'badly so indeed' is the wordplay.
'badly' indicates anagramming the letters.
'so'+'indeed'='soindeed'
'soindeed' with letters rearranged gives 'ONE-SIDED'.
(Other definitions for one-sided that I've seen before include "So denied being unfair or biased" , "Partial" , "Unfair, unequal" , "Indeed so (anag.)" , "Grossly unequal; biased" .)