Straightforward, simple (4)
I believe the answer is:
easy
I believe this is a double definition.
'straightforward' is the first definition.
(easy can mean straightforward or simple)
'simple' is the second definition.
(similar in meaning)
(Other definitions for easy that I've seen before include "... Rider (film)" , "Posing no difficulty" , "for a piece of cake" , "Tranquil" , "Like a walk in the park?" .)