What diner orders contains an off-colour dairy product (6,4)
I believe the answer is:
danish blue
'dairy product' is the definition.
(Danish blue is an example)
'what diner orders contains an off-colour' is the wordplay.
I cannot really see how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is present in the answer.
'colour' could be 'blue' (blueing is a kind of colouring) and 'blue' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for danish blue that I've seen before include "possibly crackers with it" , "served up on board?" .)