Frank, straightforward (6)
I believe the answer is:
candid
I believe this is a double definition.
'frank' is the first definition.
(synonyms)
'straightforward' is the second definition.
(I've seen this before)
(Other definitions for candid that I've seen before include "Free and frank" , "Frank, forthright" , "Plain" , "Frank, honest" , "Blunt; frank" .)