Legitimate, proper (6)
I believe the answer is:
kosher
This clue is a double definition.
'legitimate' is the first definition.
(I've seen this in another clue)
'proper' is the second definition.
(I've seen this before)
(Other definitions for kosher that I've seen before include "Conforming to Jewish dietary law" , "Genuine and legitimate (informal)" , "Edible for Jew" , "Of food, conforming to requirements of Jewish law" , "Legitimate (according to Jewish law?)" .)