What does ‘shines’ mean in “Bears defense shines in 24-17 loss to Panthers”?
It means sense 3 of the OED, to perform very well: the Bears lost the match, even though their defence "performed very well". There are more aspects to a match than just your defence. Apparently the Panthers did better in other respects.
It should probably appear as a fourth definition:
v. To be the single bright spot in an otherwise dismal situation.
It's used in this sense fairly often, but only in journalism and usually in the sports section.
In this case, "shines" means "stands out", "its high quality is on display".