"clear challenge" is grammatically correct and can be used in written English.
For example, "The company faced a clear challenge when they tried to increase their market share."
"What happened yesterday is a clear challenge," said Ernesto Borda, a political analyst in Bogotá.
The gambit also poses a clear challenge to the United States.
It is a clear challenge to Italian center-left leader Pier Luigi Bersani.
That big ambition sets a clear challenge to other governments, foundations and companies.
To this clear challenge some leading rationalists have replied as follows: (1) positivists have confused real with verbal definition.
Furthermore, given the lack of any clear challenge to his leadership, he had no need for such histrionics.
As a leader of Eastern Christianity, the patriarch of Constantinople represented a clear challenge to the universalist claims of Rome.
Energy was already a clear challenge for Toyota – you can't be in manufacturing and not deal with rising energy costs.
One of the overlooked aspects of the coming reforms to higher education is the clear challenge to its leaders.
Irish governance failings are many, but the institutions of state function, particularly when faced with a clear challenge.
This is a clear challenge for both academia and industry to gain the required knowledge to design and develop new and improved catalysts.
