Claim it's a rave-up (4)

I believe the answer is:

aver

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'claim' is the definition.
(aver means to state or claim something)

'its a rave-up' is the wordplay.
'rave' anagrams to 'AVER'.
However, I'm unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for aver that I've seen before include "'Affirm, assert (4)'" , "State firmly, perhaps rave" , "State (to be the case)" , "State firmly - even rave about" , "Declare < old cattle" .)

I've seen this clue in The Irish Independent.

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