Stopping chorus with gin cocktail (10)

'stopping' is the definition.
The definition and answer can be both to do with fundamental existence as well as being present participle verbs.
Perhaps you can see a link between them that I can't see?

'chorus with gin cocktail' is the wordplay.
I cannot quite see how this works, but
'chorus' could be 'refrain' (synonyms) and 'refrain' is located in the answer.
an anagram of 'gin' is 'ing' which is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?