Make a cat sit still (6)
I believe the answer is:
'still' is the definition.
(static can mean still or not moving)
'make a cat sit' is the wordplay.
'make' indicates anagramming the letters.
'catsit' anagrammed gives 'STATIC'.
(Other definitions for static that I've seen before include "Unmoving, still" , "Constant interference" , "irritation for the listener?" , "Inert, motionless" , "Inactive, motionless" .)