Way of shifting reserve vessel (10)

I believe the answer is:

icebreaker

I believe this is a double definition.

'way of shifting reserve' is the first definition.

'vessel' is the second definition.
(icebreaker is a kind of vessel)

(Other definitions for icebreaker that I've seen before include "useful at beginning of party?" , "Something to relax social tension" , "Conversation starter" , "Ship clearing channel" , "Something relieving initial tension" .)

I've seen this clue in The Times.

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