Baseball hats (4)
I believe the answer is:
caps
'baseball hats' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for caps that I've seen before include "Coverings, for heads say" , "Coverings for heads or bottles" , "Imposes limits on" , "Crowns" , "Headgear for internationals" .)