Submarine endures a buffeting (8)

I believe the answer is:

undersea

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

'submarine' is the definition.
(submarine means under the sea)

'endures a buffeting' is the wordplay.
'endures a' can be anagrammed to 'UNDERSEA'.
However, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for undersea that I've seen before include "Below marine surface" , "submerged" , "in salt water" , "Beneath the oceans" , "Where bed is" .)

I've seen this clue in The Irish Independent.

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