Bright; cheerful (5)
I believe the answer is:
sunny
I believe this is a double definition.
'bright' is the first definition.
(similar in meaning)
'cheerful' is the second definition.
(similar in meaning)
(Other definitions for sunny that I've seen before include "(Of a person's disposition) always positive" , "Bright and cheerful" , "Genial, cheerful" , "cheerful sound" , "Bright and warm" .)