Stadium hosting second large club (7)
I believe the answer is:
arsenal
'club' is the definition.
(I've seen this before)
'stadium hosting second large' is the wordplay.
'stadium' becomes 'arena' (eg a sports arena).
'hosting' means one lot of letters goes inside another (inserted letters are welcomed in or hosted).
'second' becomes 's' (common abbreviation).
'large' becomes 'L' (eg in clothes sizes).
'arena' going around 's' is 'arsena'.
'arsena'+'l'='ARSENAL'
(Other definitions for arsenal that I've seen before include "Ammunition store or English soccer team" , "Supply of weapons" , "Armoury - London football club" , "English football club and military depot" , "Football team - magazine" .)