Unbalanced United team finally defeated (3-5)
I believe the answer is:
one-sided
'unbalanced' is the definition.
(I've seen this before)
'united team finally defeated' is the wordplay.
'united' becomes 'one' (as in a phrase like 'we are one').
'team' becomes 'side' (both can mean a sports team).
'finally' suggests the final letters.
The last letter of 'defeated' is 'd'.
'one'+'side'+'d'='ONE-SIDED'
(Other definitions for one-sided that I've seen before include "Unfair, unequal" , "Unfairly biased" , "Unequal like contest between badly matched opponents" , "Indeed so (anag.)" , "Unilateral" .)