Cap on pike production (4)
I believe the answer is:
kepi
'cap' is the definition.
(I know that kepi is a type of cap)
'pike production' is the wordplay.
'production' indicates anagramming the letters.
'pike' with letters rearranged gives 'KEPI'.
'on' is the link.
(Other definitions for kepi that I've seen before include "French army cap" , "Military cap with circular top" , "Service cap" , "French military cap" , "Flat-topped military cap" .)