Possibly first signs of disunity (5)

I believe the answer is:

rifts

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'signs of disunity' is the definition.
Although both the answer and definition are plural nouns, I cannot see how one could define the other.

'possibly first' is the wordplay.
'possibly' indicates an anagram.
'first' with letters rearranged gives 'RIFTS'.

Can you help me to learn more?

(Other definitions for rifts that I've seen before include "Splits" , "Deep divides" , "Schisms" , "Breaks, severances" , "Clefts in earth, or disagreements" .)

I've seen this clue in the Evening Standard.

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