Still, has turned it into a musical (6)
I believe the answer is:
static
'still' is the definition.
(static can mean still or not moving)
'turned it into a musical' is the wordplay.
'turned' is a reversal indicator.
'into' means one lot of letters goes inside another.
'a musical' becomes 'Cats' (Andrew Lloyd Webber musical).
'it' going into 'cats' is 'citats'.
'citats' reversed gives 'STATIC'.
'has' acts as a 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" .)