He may march to his music (5)
I believe the answer is:
piper
'his music' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he may march' is the wordplay.
'he' becomes 'Pip'.
'may march' becomes 'er' (I am not sure about this - if you are sure you should believe this answer much more).
'pip'+'er'='PIPER'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for piper that I've seen before include "Wind instrumentalist" , "Musician sometimes paid (or pied!)" , "Instrumentalist, solo or military" , "who puffs out his cheeks?" , "Military musician" .)