Wine on demand at last (3)
I believe the answer is:
red
'wine' is the definition.
(red is a type of wine)
'on demand at last' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'at last' indicates one should take the final letters.
The final letter of 'demand' is 'd'.
're'+'d'='RED'
(Other definitions for red that I've seen before include "Inflamed" , "socialist?" , "Looking embarrassed" , "Stop light" , "Colour of 1 across" .)