ADJ in n
The use of an adjective followed by in is productive. Adjectives which indicate how someone behaves in a particular situation also have this pattern. They include active, flexible, generous, honest, innovative, lavish, scathing, serious, and sincere.
They were active in the provision of health care and education, and they gave poor people dignity and hope.
The noun group often begins with a possessive determiner.
She is a graduate of Chelsea College of Art and is innovative in her use of oil paints.
She was scathing in her comments on the hypocrisies of English class, but tolerant of human weaknesses.
Mr Brooke is convinced that the political parties are serious in their desire for negotiations.