Biden, half-intoxicated, gulping large drop back (4,6)

I believe the answer is:

fall behind

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'drop back' is the definition.
'fall behind' can be an answer for 'back' (thesaurus). I am not sure about the 'drop' bit.

'biden half-intoxicated gulping large' is the wordplay.
'intoxicated' indicates an anagram.
'gulping' indicates putting letters inside (gulp can mean to swallow or consume).
'large' becomes 'L' (eg in clothes sizes).
'biden'+'half'='bidenhalf'
'bidenhalf' anagrammed gives 'falbehind'.
'falbehind' going around 'l' is 'FALL BEHIND'.

Can you help me to learn more?

(Another definition for fall behind that I've seen is " Lag".)

I've seen this clue in The Guardian.

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