Frank, careless (9)
I believe the answer is:
unguarded
This clue is a double definition.
'frank' is the first definition.
(thesaurus)
'careless' is the second definition.
(thesaurus)
(Other definitions for unguarded that I've seen before include "Imprudent" , "like man liable to be taken on board" , "Not protected" , "Open to attack" .)