A pilsner drunk by German back on the sauce? (9)

I believe the answer is:

relapsing

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'back on the sauce?' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's a link between them I don't understand?

'a pilsner drunk by german' is the wordplay.
'drunk' indicates an anagram.
'by' means one lot of letters go next to another.
'german' becomes 'g' (abbreviation).
'a'+'pilsner'='apilsner'
'apilsner' anagrammed gives 'relapsin'.
'relapsin'+'g'='RELAPSING'

Can you help me to learn more?

(Another definition for relapsing that I've seen is " sinking".)

I've seen this clue in The Independent.

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