Classic headgear (5)
I believe the answer is:
derby
This clue is a double definition.
'classic' is the first definition.
(Derby City Classic pool tournament)
'headgear' is the second definition.
(I know that derby is a type of hat)
(Other definitions for derby that I've seen before include "20 horse 12" , "Commotion" , "close match?" , "Flat race; hat" , "Canadian bowler" .)