"serious call" is a correct and usable phrase in written English.
You might use it to describe an urgent demand for action, such as: "The mayor issued a serious call to citizens to stay home and practice social distancing."
At the height of the Beltway sniper terror in Washington, there was no serious call for gun control.
Any serious call for reform has to acknowledge the severe institutional damage that has been done to the nation's regulatory agencies.
While several counties, including Britain, have decided to not send ministers or other dignitaries to Russia to attend the Games there has been no serious call for boycotts.
"Tsipras only way to make Greece's creditors malleable to his policy is to default on the debt and make a serious call to take the country out of the euro.
At one of the company's rare meetings with Wall Street analysts recently, Exxon executives boasted it had a serious call from investment bankers acting on behalf of distressed oil companies looking for a saviour.
I can't quarrel with that, but will he follow this up with a serious call to the auto industry to make more fuel-efficient cars, and a call to encourage and finance a major effort for alternative-energy sources?
Responses to less serious calls have also improved significantly.
I'm curious about how photography became a serious calling for you.
And there are very rarely serious calls for people with these criminal records to step down.
Things were getting serious: calls poured in from Washington, New York, London, Doha, Brussels.
As children's minister, she faced serious calls to quit over accusations Islington council had ignored allegations of child abuse.
