Alarm caused by our sea becoming rough (6)

I believe the answer is:

arouse

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'alarm' is the definition.
(I know that alarm is a more specific form of the action affright)

'our sea becoming rough' is the wordplay.
'our sea' can be anagrammed to 'AROUSE'.
However, I'm not clear how the anagram is indicated.

'caused by' is the link.

Can you help me to learn more?

(Other definitions for arouse that I've seen before include "Wake or stir up" , "Evoke (a feeling)" , "excitement" , "Excite; wake from sleep" , "Energise" .)

I've seen this clue in The Globe and Mail.

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