Knight, courageous one, experiencing change of heart gets cut (7)
I believe the answer is:
sirloin
'cut' is the definition.
(sirloin is a kind of cut)
'knight courageous one' is the wordplay.
'knight' becomes 'sir' (a knight has the title Sir).
'courageous one' becomes 'loin' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sir'+'loin'='SIRLOIN'
'experiencing change of heart gets' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sirloin that I've seen before include "Choice cut of beef" , "(Knighted?) cut of meat" , "Upper part of loin of beef" , "Type of steak" , "Joint of beef" .)