Go down in reserve team? (7)
I believe the answer is:
subside
'go down' is the definition.
(subsiding is a kind of going down)
'reserve team?' is the wordplay.
'reserve' becomes 'sub' (I've seen this in other clues).
'team?' becomes 'side' (I've seen this before**).
'sub'+'side'='SUBSIDE'
'in' is the link.
(Other definitions for subside that I've seen before include "Wear off or die down" , "Sink to a lower level" , "(Flood) go down" , "Diminish" , "(Of floods) go down" .)