Cheerful, like Blighty, and flighty? (5-7)
I believe the answer is:
light-hearted
I believe this is a double definition.
'cheerful' is the first definition.
(I've seen this before)
'like blighty and flighty?' is the second definition.
('light' is at the heart of the words)
(Other definitions for light-hearted that I've seen before include "Cheerful, unserious" , "Free from anxiety" , "Airy and carefree" , "Happy-go-lucky" , "Playful" .)