Conduct or comport oneself (6)
I believe the answer is:
behave
I believe this is a double definition.
'conduct' is the first definition.
(I know that conduct can be written as behave)
'comport oneself' is the second definition.
(I've seen this before)
(Other definitions for behave that I've seen before include "Act in a certain way" , "Act correctly" , "Spanish peninsula" , "Act in a specified way" , "Act or react - show good manners" .)