Having a key, in music (5)
I believe the answer is:
tonal
'having a key in music' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tonal that I've seen before include "Relating to music using conventional harmony" , "Relating to conventional keys and harmonies" , "According to musical key" , "Written in conventional keys and harmony" , "of sound quality" .)