The height a bet can go up to (4)
I believe the answer is:
etna
'the height' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for etna that I've seen before include "Neat kind of European volcano" , "Europe's highest active volcano" , "source of fumes?" , "Volcanic mount in Sicily" , "Volcano in Sicily, quite neat" .)