Stadium beside lake accommodates second team (7)
I believe the answer is:
arsenal
'team' is the definition.
(Arsenal football club)
'stadium beside lake accommodates second' is the wordplay.
'stadium' becomes 'arena' ('arena' can be a synonym of 'stadium').
'beside' means one lot of letters go next to another (I've seen this in other clues).
'lake' becomes 'l'.
'accommodates' indicates putting letters inside.
'second' becomes 's' (common abbreviation).
'arena'+'l'='arenal'
'arenal' enclosing 's' is 'ARSENAL'.
(Other definitions for arsenal that I've seen before include "weapons are kept here" , "Eleven" , "gunners, so-called" , "Munitions store and English football team" , "Supply of weapons" .)