I’m doing role at sea? On canal, more likely (9)

I believe the answer is:

gondolier

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

'sea? on canal more likely' is the definition.
I can't tell whether this defines the answer.

'i'm doing role' is the wordplay.
'doing role' anagrams to 'GONDOLIER'.
However, I'm unsure how the anagram is indicated.

'at' acts as a link.

Can you help me to learn more?

(Other definitions for gondolier that I've seen before include "Craftsman" , "Venetian waterman" , "One to move over water" , "Singular SO" , "to leave Red Lion disorientated" .)

I've seen this clue in The Independent.

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