Proper, fitting (6)
I believe the answer is:
seemly
This clue is a double definition.
'proper' is the first definition.
(similar in meaning)
'fitting' is the second definition.
(I've seen this in another clue)
(Other definitions for seemly that I've seen before include "Appropriate" , "Decent - handsome" , "Fitting" , "Decorous or proper" , "Decorous, in good taste" .)