Change of policy: you are to arrest visiting solicitor (9)
I believe the answer is:
turnabout
'change of policy' is the definition.
'you are to arrest visiting solicitor' is the wordplay.
'you are' becomes 'ur' (text or internet abbreviation).
'to arrest' becomes 'nab' ('nab' can be a synonym of 'arrest').
'visiting' means one lot of letters goes inside another.
'solicitor' becomes 'tout' (I've seen this before).
'ur'+'nab'='urnab'
'urnab' inserted inside 'tout' is 'TURNABOUT'.
(Other definitions for turnabout that I've seen before include "That makes a change" , "complete change of policy" , "Total change of policy" , "change of heart" .)