Strike holding to firm limit (3-3)

I believe the answer is:

cut-off

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Another definition for cut-off that I've seen is " Point after which something is no longer effective".)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app