Making a cat sit still (6)
I believe the answer is:
static
'still' is the definition.
(static can mean still or not moving)
'making a cat sit' is the wordplay.
'making' indicates an anagram.
'cat'+'sit'='catsit'
'catsit' with letters rearranged gives 'STATIC'.
(Other definitions for static that I've seen before include "Motionless like some kind of electricity" , "it can shock and > ruin the reception" , "Atmospheric disturbance" , "fixed" , "TV or radio interference" .)