Changing beat, I stay on ground to cover new cop (11)
I believe the answer is:
syncopation
'changing beat' is the definition.
(musical process of varying a beat)
'i stay on ground to cover new cop' is the wordplay.
I cannot quite see how this works, but
'i' could be 'a' and 'a' is located in the answer.
'on' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is found within the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for syncopation that I've seen before include "Offbeat musical rhythm" , "Playing notes off the beat" , "Rhythm modification" , "Displacement of beats in music" , "Altering of musical rhythm by displacing accents" .)