Ordered ace Merlot -- one will turn up eventually (9)
I believe the answer is:
latecomer
'one will turn up eventually' is the definition.
(a latecomer arrives late)
'ordered ace merlot' is the wordplay.
'ordered' indicates an anagram.
'ace'+'merlot'='acemerlot'
'acemerlot' is an anagram of 'LATECOMER'.
(Other definitions for latecomer that I've seen before include "Recent convert" , "Unpunctual type o" , "Delayed arrival" , "one's a poor timekeeper" , "Recent or tardy arrival" .)