'Relatively calm' perhaps is a label at sea (8)

I believe the answer is:

sailable

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'relatively calm' is the definition.
The definition suggests an adjective which matches the answer.

'is a label at sea' is the wordplay.
'at sea' is an anagram indicator.
'is'+'a'+'label'='isalabel'
'isalabel' with letters rearranged gives 'SAILABLE'.

'perhaps' acts as a link.

Can you help me to learn more?

(Other definitions for sailable that I've seen before include "Tartans should be so" , "Like schooners" .)

I've seen this clue in The Guardian.

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