Noun
mountain to climb (plural mountains to climb)
A difficult challenge.
She was a girl with a mountain to climb. Markus Zusak
Whoever gets himself elected President in 2010 will have a steep mountain to climb. Francis Escudero
It is my desire to be a great writer. I know that I still have a mountain to climb to achieve that. Guy Johnson
I'm one of those people who always needs a mountain to climb. When I get up a mountain as far as I think I'm going to get, I try to find another mountain. Polly Bergen