Fish and chips on desk to start with (3)
I believe the answer is:
cod
'fish' is the definition.
(type of fish)
'chips on desk to start with' is the wordplay.
'to start with' indicates taking the first letters.
The first letters of 'chips on desk' is 'COD'.
'and' is the link.
(Other definitions for cod that I've seen before include "A fish; a hoax, parody" , "Pay when you get the goods - sounds fishy" , "Edible fish" , "method of payment" , "faked" .)