Understanding 彼はこの分野で五指を屈する内に入る I was reading the definition of : > > > ①―― ― I don't understand this example sentence > I think it roughly means he entered the stage where he needs to clench his fingers into a fist in this field? I am uncertain about the meaning of here. I wonder in what context will this sentence will make sense? Baseball?

Note the definition:

>

It refers to the act of bending fingers to count (counting on your fingers).

means bending fingers up to 5. 'He' is counted before count 5, so the sentence means _he is within world-class top 5 in this field_.