It's better when princes have a change of heart (5)
I believe the answer is:
nicer
'it's better' is the definition.
(I've seen this before)
'princes have a change of heart' is the wordplay.
'princes have' becomes 'nic' (I can't justify this - if you can you should give a lot more credence to this answer).
'a change' becomes 'jerk' (jerk is a kind of change).
'of heart' means to look at the middle letters (I've seen 'hearts' mean this).
The middle of 'jerk' is 'er'.
'nic'+'er'='NICER'
'when' is the link.
Can you help me to learn more?
(Other definitions for nicer that I've seen before include "harder to please" , "Pleasanter" , "More pleasant or courteous" , "better" , "More pleasing" .)