Look! Doctor's about to be tuneful (7)
I believe the answer is:
melodic
'be tuneful' is the definition.
(I've seen this in another clue)
'look doctor's about' is the wordplay.
'look' becomes 'lo' (archaic exclamation meaning 'look!').
'doctor' becomes 'medic' (doctor is a type of medic).
'about' is an insertion indicator.
'lo' placed into 'medic' is 'MELODIC'.
'to' is the link.
(Other definitions for melodic that I've seen before include "Harmonious" , "Pleasant-sound" , "nice on the ear" , "Old mice (anag.)" , "Pleasantly musical" .)