Embellishment of drink service (7)
I believe the answer is:
necklet
'embellishment' is the definition.
(accessory or embellishment worn round the neck)
'drink service' is the wordplay.
'drink' becomes 'neck' (to neck a drink is to drink it quickly).
'service' becomes 'let' (type of tennis serve).
'neck'+'let'='NECKLET'
'of' is the link.
(Other definitions for necklet that I've seen before include "Something ornamental" , "Ornament worn above shoulder level" , "Ornament worn below the chin" , "Little ornament" , "Something like a choker" .)