In Hull City's old stadium (10)
I believe the answer is:
hippodrome
'old stadium' is the definition.
(ancient Greek stadium)
'in hull city's' is the wordplay.
'in' becomes 'hip' (both can mean fashionable).
'hull' becomes 'pod' (both can mean a case or shell).
'city' becomes 'rome' (Rome is an example).
'hip'+'pod'+'rome'='HIPPODROME'
(Other definitions for hippodrome that I've seen before include "Stadium for horse shows or horse races" , "Chariot racetrack" , "Ancient Greek course" , "old track" , "Theatre (originally for horse racing)" .)