Crossword Genius

What's often depressed after a period? (5,3)

Ross

I believe the answer is:

space bar

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?

(Other definitions for space bar that I've seen before include "Long key on a typewriter" , "Longest typing key" , "key, large one" , "Keyboard key" , "The biggest typewriter key" .)

I've seen this clue in The Times.
Want a hint initially instead of a full solution? Install my app