Arch in use by marine creature (3,6)

I believe the answer is:

sea urchin

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

'marine creature' is the definition.
(I've seen this before)

'arch in use' is the wordplay.
'arch in use' anagrams to 'SEA URCHIN'.
Though, I'm not sure how this is indicated.

'by' is the link.

Can you help me to learn more?

(Other definitions for sea urchin that I've seen before include "Echinoderm with a thin spiny globular shell" , "Shelled marine creature" , "Marine invertebrate with spikes" , "prefers salt water" , "Marine animal with globular body" .)

I've seen this clue in The Irish News.

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