A relaxing beginning to a formal atmosphere in a ship sailing the Arctic seas (10)
I believe the answer is:
icebreaker
'a relaxing beginning' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for icebreaker that I've seen before include "Something helping to start a conversation" , "Chatty partygoer without reserve" , "useful at beginning of party?" , "Reinforced vessel" , "which opens dialogue?" .)