A team not taken into account (5)
I believe the answer is:
aside
'not taken into account' is the definition.
('aside' can be a synonym of 'not taken into account')
'a team' is the wordplay.
'team' becomes 'side' (I've seen this before).
'a'+'side'='ASIDE'
(Other definitions for aside that I've seen before include "Line spoken to the audience of a play" , "Actor's line directed solely to audience" , "Quiet words spoken" , "In reserve; actor's remark to audience" , "Privately, apart" .)