Repeatedly on cruises at sea as an expert (11)
I believe the answer is:
connoisseur
'expert' is the definition.
(I know that connoisseur is a type of authority)
'repeatedly on cruises at sea as an' is the wordplay.
I cannot really see how this works, but
'on' is present in the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for connoisseur that I've seen before include "discriminating judge" , "Expert judge of taste" , "Knowledgeable art-lover" .)