Old Vlad in the Netherlands climbing? Only it's flat! (5,4)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Reversal of ( … climbing , in a down clue) [ O(abbrev. for “old”) + ME(Vlad, our setter using the self-referential pronoun) contained in ( in ) NL(ISO 3166 code for the Netherlands) ] + SOLE(the one and only).