I think this is/was a paddock to keep sheep in off the mountain so the "shelter" part is the drystone wall (perhaps @rupertmaesglas can help)

If its not in use any more (the walls look damaged) the tags should have lifecycle prefixes. I'm not really sure what the lifecycle tags should be but perhaps something like
landuse=meadow,
meadow=paddock
With a note to say its use might be more appropriate?