On the menu, it's ony so high (4)

I believe the answer is:
soup
'on the menu it's ony' is the definition.
I can't tell whether this defines the answer.
'so high' is the wordplay.
'high' becomes 'up' (associated in meaning).
'so'+'up'='SOUP'
Can you help me to learn more?
(Other definitions for soup that I've seen before include "Preliminary course" , "Stolen plate melted down" , "Eg, minestrone" , "Photographic developer" , "Eskimo people" .)
