One swoops low moving left to right (3)

I believe the answer is:

owl

I'm a little stuck... Click here to teach me more about this clue!

'one swoops' is the definition.
(I've seen this before)

'low moving left to right' is the wordplay.
'low' anagrams to 'OWL'.
However, I am not clear how this is indicated.

Can you help me to learn more?

(Other definitions for owl that I've seen before include "paragon of wisdom?" , "Athena's bird" , "Night hunter" , "One swoops" , "Wise old night-flier" .)

I've seen this clue in The Sun.

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