This is a quote from the Wikipedia page for Freddie Mercury.
[Freddie Mercury] did a commendable job of stretching into uncharted territory.
Could someone tell me what does "stretching into" mean?
Dictionary definition of stretching: To cause to extend from one place to another or across a given space. This, however, is not what it means in this sentence. This word is used in this sentence as somewhat a metaphor. Basically, it comes from the idea that stretching something makes it more tense and uses more energy to stretch it out further. The sentence is saying that Freddy Mercury put extra effort into getting into uncharted territory. So, in short, [Freddie Mercury] did a commendable job of (putting extra effort into reaching) uncharted territory.