Open, frank (6)
I believe the answer is:
candid
I believe this clue is a double definition.
'open' is the first definition.
(I know that open can be written as candid)
'frank' is the second definition.
(synonyms)
(Other definitions for candid that I've seen before include "Free and frank" , "Truthful and straightforward" , "Frank - open" , "Frank - and CID (anag)" , "Blunt; frank" .)