What Dennis Hopper has in store (4)
I believe the answer is:
shop
'store' is the definition.
(I know that store can be written as shop)
'what dennis hopper has' is the wordplay.
'has' says the answer is hidden in the clue.
'SHOP' can be found hidden inside 'what dennis hopper'.
'in' is the link.
(Other definitions for shop that I've seen before include "Inform on (slang)" , "Retail outlet" , "Give away" , "Establishment for the sale of goods" , "Store - grass up" .)