This is the 560th most frequent Dutch word.
flinke
"Flinke" means "considerable," "significant," or "substantial" in English, depending on the context.
In this sentence, 'flinke' is used as an adjective meaning 'significant' or 'serious', modifying the noun 'fout' (mistake).
Hij maakte een flinke fout.
He made a significant mistake.
Here, 'flinke' describes the intensity of 'regenbui' (rain shower) as 'heavy' or 'considerable'.
Er viel een flinke regenbui vanochtend.
There was a heavy rain shower this morning.
Here, 'flink' (the base form from which 'flinke' derives) is used as an adverb meaning 'considerable' or 'intense', describing the nature of the work.