Senior cop involved in settlement dispute (10)
I believe the answer is:
contradict
'dispute' is the definition.
(I've seen this before)
'senior cop involved in settlement' is the wordplay.
'senior cop' becomes 'di' (detective inspector).
'involved in' indicates putting letters inside.
'settlement' becomes 'contract' (I've seen this before).
'di' inserted into 'contract' is 'CONTRADICT'.
(Other definitions for contradict that I've seen before include "Deny" , "Be in conflict with" , "Assert the opposite of (a statement)" , "Gainsay" , "Refute" .)