Ocker upset about silver service charge (7)
I believe the answer is:
corkage
'service charge' is the definition.
(corkage is a kind of service charge)
'ocker upset about silver' is the wordplay.
'upset' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'ocker' anagrammed gives 'corke'.
'corke' going around 'ag' is 'CORKAGE'.
(Other definitions for corkage that I've seen before include "Fee charged by restaurants for serving wine brought by customers" , "Charge for bringing own wine to restaurant" , "Restaurant's charge for bringing own wine" .)