Express back to Waterloo departing midday's best (3-4)
I believe the answer is:
non-stop
'express back' is the definition.
Both the definition and answer are adverbs. Perhaps you can see an association between them that I don't see?
'waterloo departing midday's best' is the wordplay.
I cannot quite see how this works, but
'midday's' could be 'ns' (abbreviation for noon) and 'ns' is found in the answer.
'best' could be 'top' (top can mean the very best) and 'top' is present in the answer.
The remaining letters 'no' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for non-stop that I've seen before include "Uninterrupted" , "Continuous" , "Going straight from A to B" , "Round-the-clock" , "Unceasing" .)