Crossword Genius

Provide a couple of bits of variety (4)

Ross

I believe the answer is:

vary

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'provide' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how they can define each other.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for vary that I've seen before include "Fluctuate" , "Differ, alter" , "Differ from a standard" , "Change form or state" , "Diversify" .)

I've seen this clue in the Evening Standard.
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