Prohibit part of garden? Yes (4)
I believe the answer is:
deny
'prohibit' is the definition.
(thesaurus)
'part of garden? yes' is the wordplay.
'part of' indicates a hidden word.
'DENY' is hidden within 'garden yes'.
(Other definitions for deny that I've seen before include "Refuse to give" , "Repudiate, disavow" , "Refuse to grant" , "Refuse to acknowledge" , "Refuse to admit the truth" .)