Is zero such a number? (5)
I believe the answer is:
round
'a number?' is the definition.
(I have seen 'number of drinks' mean 'round' so perhaps 'number' could also mean 'round')
'is zero' is the wordplay.
I cannot quite see how this works, but
'zero' could be 'o' (O resembles 0) and 'o' is found within the answer.
The remaining letters 'rund' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'such' is the link.
Can you help me to learn more?
(Other definitions for round that I've seen before include "Circular - 18 holes" , "delivery trip?" , "Serving of sandwich" , "unsuitable for square pegs" , "Spherical; song" .)