Support team that’s bottom (8)
I believe the answer is:
'bottom' is the definition.
(I've seen this before)
'support team' is the wordplay.
'support' becomes 'back' (back is a kind of support).
'team' becomes 'side' (I've seen this before).
'that's' is the link.
(Other definitions for backside that I've seen before include "Behind" , "Hind part" , "Rear" , "Bottom" , "Buttocks" .)