Pet adder gone astray — it happened earlier (8)

I believe the answer is:

predated

'happened earlier' is the definition.

'pet adder gone astray' is the wordplay.
'gone astray' indicates an anagram (I've seen this in other clues).
'pet'+'adder'='petadder'
'petadder' is an anagram of 'PREDATED'.

'it' is the link.
I am not very happy about this link. It may belong to another bit of the clue.

I've seen this clue in The Guardian.

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