Shelter from what the swingers hope to avoid (6)

I believe the answer is:

bunker

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'shelter' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for bunker that I've seen before include "Golfing 1 ac" , "Sand trap" , "at the golf club?" , "Wartime shelter" , "Underground shelter, store" .)

I've seen this clue in the Irish Times.

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