Place to holiday before Day of Judgement - only to be used if all else fails (4,6)
I believe the answer is:
last resort
'place' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps there's a link between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for last resort that I've seen before include "When all else fails, try this" , "Final expedient" , "when everything else has failed?" .)