To growl at one’s sweetheart is the wrong thing to do (3)

I believe the answer is:

err

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'do' is the definition.
The answer and definition can be both to do with motion as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for err that I've seen before include "Bungle" , "Transgress" , "'To . . . is human, to forgive divine'" , "'to... is human,to forgive divine'" , "Miscalculate" .)

I've seen this clue in the Evening Standard.

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