Run about in empty garden (6)
I believe the answer is:
'run' is the definition.
(both can mean to rule over)
'about in empty garden' is the wordplay.
'about' becomes 'over' (both can mean around).
'in' indicates putting letters inside.
'empty' says to hollow out the word (remove centre letters).
'garden' with its middle taken out is 'gn'.
'over' placed within 'gn' is 'GOVERN'.
(Other definitions for govern that I've seen before include "Rule with authority, perhaps a country" , "Control, influence" , "Run" , "Control and direct the affairs of" , "Manage - control" .)