Lists birds -- around 50 (5)

I believe the answer is:

tilts

'lists' is the definition.
(I've seen this in another clue)

'birds around 50' is the wordplay.
'birds' becomes 'tits' (tit is a kind of bird).
'around' indicates putting letters inside.
'50' becomes 'l' (Roman numeral).
'tits' going around 'l' is 'TILTS'.

I've seen this clue in The Telegraph.

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