Brown toast and nothing on top (3)
I believe the answer is:
tan
'brown' is the definition.
(tan is a kind of brown)
'toast and nothing on top' is the wordplay.
'on top' indicates taking the first letters.
The initial letters of 'toast and nothing' is 'TAN'.
(Other definitions for tan that I've seen before include "Yellow-brown colour" , "function" , "Shade of brown" , "belt" , "Light brown colour" .)