Stadium souvenir
I believe the answer is:
cap
'stadium souvenir' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cap that I've seen before include "Protective lid" , "Set limit to price increase - of headgear?" , "Surpass with headwear" , "Outdo; brimless hat" , "Upper limit; hat" .)