Regulated melody, on the day (5)
I believe the answer is:
tuned
'regulated melody on the day' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Maybe you can see an association between them that I can't see?
'melody on the day' is the wordplay.
'melody' becomes 'tune' ('tune' can be a synonym of 'melody'**).
'on' is a charade indicator (letters next to each other).
'the day' becomes 'd'.
'tune'+'d'='TUNED'
Can you help me to learn more?
(Other definitions for tuned that I've seen before include "arranged for reception" , "Adjusted (musical) pitch" , "desired pitch" , "Got engine right" , "on song" .)