Appear to support team in subordinate event (8)
I believe the answer is:
sideshow
'subordinate event' is the definition.
(I've seen this before)
'appear to support team' is the wordplay.
'appear' becomes 'show' (showing is a kind of appearing).
'to support' means one lot of letters go next to another (in a down clue, some letters hold others up).
'team' becomes 'side' (both can mean a sports team).
'show' after 'side' is 'SIDESHOW'.
'in' is the link.
(Other definitions for sideshow that I've seen before include "Minor display adjacent to a larger one" , "Subordinate production to the main event" , "Activity subordinate to a larger one" , "Exhibition subordinate to a larger one" , "affair at a fair" .)