"idle fear" is correct and usable in written English.
It is an expression used to describe a fear that does not have a real basis, like a baseless fear or anxiety without a real cause. For example, "The crowd was filled with idle fear, despite there being no real danger."
This is no idle fear, Mr. Gingrich warns in his book: "The secular-socialist machine represents as great a threat to America as Nazi Germany or the Soviet Union once did".
While the government would not arrest them until more than a decade later, it was no idle fear: The trader who federal prosecutors say turned the lawyer's tips into $32 million in illicit profits had been accused of insider trading by a brokerage firm that year.
If no help is forthcoming, there is every chance that the ensuing economic chaos, in the wake of a likely rouble crash, will not only bring down the current government but may even bring down Russia's rough-and-ready democracy.This is no idle fear (see article).
Though the non-gene part of the genome is often dismissed as mere "junk DNA", they felt (correctly) that at least some of it must be biologically important, so disentangling the whole lot was therefore necessary.That turned out to be an idle fear.
This is not an idle fear.
Stranger— Beneath this Cone in unconscrated Ground A Friend to the Liberties of mankind Directed his Body to be Inhum'd May the Example Contribute to Emancipate thy mind From the Idle Fears of Superstition And the wicked arts of Priesthood.
Increases in the supply of money simply add to idle balances as fear grips the economy.
And it will take effort to cast off the idle inertia and fear of awkwardness that keeps us from communicating.
It is why Robson need not fear idle comparisons with the last Australian-born opening batsman to play for England, Jason Gallian, whose Test career ended after three matches and brought an average of just 12. Neither will Ballance worry yet about a propensity to get deep in his crease and play at wide balls with feet barely moving.
But Mr. Noda also stressed that reducing Japan's dependence on nuclear power would be a gradual process, and that reactors that have fallen idle over safety fears since the Fukushima Daiichi accident would be restarted, albeit after stringent checks and gaining the understanding of local communities.
