Ready for customers (4)
I believe the answer is:
open
'ready for customers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for open that I've seen before include "Unfasten" , "Frank; not closed" , "Undo; ajar" , "Frank - ready for business" , "This championship includes both professional and amateur golfers" .)