Take down what's on the menu (3)
I believe the answer is:
eat
'take' is the definition.
(eating is a kind of taking)
'down what's on the menu' is the wordplay.
I cannot quite see how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is found in the answer.
A single letter 'e' remains 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 eat that I've seen before include "Break bread" , "Worry" , "Feed" , "to do etching?" , "Dine in a restaurant" .)