Area of filled pizza having no calories (4)
I believe the answer is:
zone
'area' is the definition.
(I know that area can be written as zone)
'of filled pizza having no calories' is the wordplay.
I cannot quite see how this works, but
'of' could be 'o' and 'o' is found within the answer.
'no' could be 'z' and 'z' is present in the answer.
The remaining letters 'ne' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for zone that I've seen before include "London Underground region" , "Area subject to restrictions, parking say" , "Area with particular characteristics" , "Region; time area" , "District, area" .)