I will explain in the easiest way possible.
Context clues are clues you find by reading the sentence. It can be words directly next to the word you are looking for, or even at the beginning or end. You are trying to figure out the meaning of scrimmage. The words that help you understand scrimmage are easy to find. During the scrimmage, the players took more chances than usual because they knew the final outcome wouldn't affect their record. From that we can assume that scrimmage could mean either a non-official game or a practice game.
I hope this helps!