Spill the beans on the lawn? (5)

I believe the answer is:

grass

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

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

I cannot understand how the remainder of the clue works.

(Other definitions for grass that I've seen before include "Inform on someone" , "something in the park?" , "Drug" , "Slang word meaning both marijuana and informant" , "Weed" .)

I've seen this clue in the Evening Standard.

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