Square meal with no starter for lunch (4)
I believe the answer is:
four
'square' is the definition.
(four is a square number)
'meal with no starter for lunch' is the wordplay.
I cannot quite understand how this works, but
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is present in the answer.
The remaining letters 'fur' 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 four that I've seen before include "IV in Roman numerals" , "Square number" , "Figure" , "10 cleared of misuse of fortune" , "Rowing boat; number" .)