Restaurant employee dropping one drink (5)
I believe the answer is:
water
'drink' is the definition.
(water is an example)
'restaurant employee dropping one' is the wordplay.
'restaurant employee' becomes 'waiter' (restaurants employee waiters).
'dropping' is a deletion indicator.
'one' becomes 'i' (Roman numeral).
'waiter' with 'i' taken away is 'WATER'.
(Other definitions for water that I've seen before include "Aqua" , "Commonplace drink" , "Superior's full of it" , "Diamond quality" , "Inundate" .)