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