Fifty-one pounds of fluids (7)

I believe the answer is:

liquids

'fluids' is the definition.
(I know this)

'fifty-one pounds' is the wordplay.
'fifty' becomes 'li' (I've seen this in other clues).
'one pounds' becomes 'quids' ('quid' can be a synonym of 'pound').
'li'+'quids'='LIQUIDS'

'of' acts as a link.

(Another definition for liquids that I've seen is " Lots of alcohol perhaps".)

I've seen this clue in the Sydney Morning Herald.

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