Be off, animals (4)

I believe the answer is:

shoo

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'be' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how one could define the other.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for shoo that I've seen before include "Shove off!" , "word of dismissal" , "Word used to frighten away animals" , "Exclamation used to chase away animals" , "Dismissive remark" .)

I've seen this clue in the Evening Standard.

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