Hermann Buhl reached the summit of ____ in 1953, in the only solo first ascent of an 8000-metre peak (5,6)

I believe the answer is:

nanga parbat

I'm a little stuck... Click here to teach me more about this clue!

'peak' is the definition.
(Nanga Parbat is an example)

I don't understand the remainder of the clue.

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app