Being unbalanced, team has done badly outside (3-5)
I believe the answer is:
one-sided
'being unbalanced' is the definition.
(I've seen this before)
'team has done badly outside' is the wordplay.
'team has' becomes 'side' (I am not sure about this - if you are sure you should believe this answer much more).
'badly' indicates an anagram (letters in the wrong order).
'outside' indicates putting letters inside.
'done' is an anagram of 'oned'.
'side' placed inside 'oned' is 'ONE-SIDED'.
Can you help me to learn more?
(Other definitions for one-sided that I've seen before include "Unfair or partisan - single dimension?" , "Biased, favouring one part over another" , "So denied being unfair or biased" , "Unbalanced" , "Unilateral" .)