Instances of continual variation (9)

I believe the answer is:

incessant

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'continual variation' is the definition.
The definition and answer are not the same part of speech.

'instances' is the wordplay.
'instances' can be anagrammed to 'INCESSANT'.
Though, I am not sure how the anagram is indicated.

'of' is the link.

Can you help me to learn more?

(Other definitions for incessant that I've seen before include "Unending" , "happening all the time" , "Since Stan was continual." , "Persistent" , "Perpetual, unremitting" .)

I've seen this clue in The Irish Independent.

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