From Longman Dictionary of Contemporary Englishgive somebody/something the green lightgive somebody/something the green lightLET/ALLOWto allow a project, plan etc to begin The government has given the green light to Sunday trading. → green light
Examples from the Corpus
give somebody/something the green light• Doctors gave him the green light yesterday to start against New Orleans on Sunday night.• Everyone has given it the green light.• The board just gave us the green light to begin research. 