Three-foot garden (4)

I believe the answer is:

yard

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

'garden' is the definition.
(I have seen 'American garden' mean 'yard' so perhaps 'garden' could also mean 'yard')

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for yard that I've seen before include "36 inches" , "3ft" , "Three feet - detectives?" , "Earth" , "Thirty six inches" .)

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