Everybody loves a posh royal, one who's an old predator? (8)

I believe the answer is:

allosaur

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'one who's an old predator?' is the definition.
I can't tell whether this defines the answer.

'everybody loves a posh royal' is the wordplay.
'everybody' becomes 'all' (all people).
'loves' becomes 'os'.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'royal' becomes 'r' (abbreviation).
'all'+'os'+'a'+'u'+'r'='ALLOSAUR'

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I've seen this clue in The Guardian.

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