Maybe onion on the counter makes you cry (4)

I believe the answer is:

blub

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

'cry' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for blub that I've seen before include "Sob without restraint" , "Cry like a child" , "Cry (colloq.)" , "Sob childishly" , "Utter while sobbing" .)

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