Fish eater ordered plaice with starter of nachos (7)
I believe the answer is:
pelican
'fish eater' is the definition.
'ordered plaice with starter of nachos' is the wordplay.
'ordered' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'starter of' says to take the initial letters.
The initial letter of 'nachos' is 'n'.
'plaice' is an anagram of 'pelica'.
'pelica'+'n'='PELICAN'
(Other definitions for pelican that I've seen before include "One presenting big bill" , "Large bird with pouch in bill for storing fish" , "Tropical bird" , "Bird with large pouched beak" , "Does its beak hold more that its belly can?" .)