Still, has turned it into a musical (6)
I believe the answer is:
static
'still' is the definition.
('static' can be a synonym of 'still')
'turned it into a musical' is the wordplay.
'turned' says the letters should be written in reverse.
'into' indicates putting letters inside.
'a musical' becomes 'cats' (I've seen this before).
'it' inserted into 'cats' is 'citats'.
'citats' reversed gives 'STATIC'.
'has' is the link.
(Other definitions for static that I've seen before include "Unmoving, still" , "Still - crackling on the radio" , "TV or radio interference" , "stable" , "Noise caused by electrical interferance" .)