Good spirits from writer having change of heart (4)
I believe the answer is:
brio
'good' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see a link between them that I don't see?
'spirits from writer having change of heart' is the wordplay.
'spirits from writer' becomes 'bro' (I can't justify this - if you can you should believe this answer much more).
'having' means one lot of letters goes inside another.
'change' becomes 'air' (air is a kind of change).
'of heart' means to look at the middle letters (I've seen 'hearts' mean this).
The middle of 'air' is 'i'.
'bro' enclosing 'i' is 'BRIO'.
Can you help me to learn more?
(Other definitions for brio that I've seen before include "Drive" , "Animation (Italian)" , "Spiritedness" , "Vigour, vivacity" , "'Liveliness, vivacity (4)'" .)