A round space in the garden that is not empty or under control (8)
I believe the answer is:
obedient
'under control' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I can't see?
'a round space in the garden that is not empty' is the wordplay.
'a round' indicates putting letters inside.
'space in the garden' becomes 'odie' (I am not sure about this - if you are sure you should believe this answer much more).
'that is' becomes 'be'.
'empty' says to hollow out the word (remove centre letters).
'not' with its centre taken out is 'nt'.
'odie' enclosing 'be' is 'obedie'.
'obedie'+'nt'='OBEDIENT'
'or' is the link.
Can you help me to learn more?
(Other definitions for obedient that I've seen before include "Doing what one is told, compliant" , "Submissive, compliant" , "Submissive, biddable" , "Following instructions" , "Docile" .)