Called round on policeman's orders (7)
I believe the answer is:
'orders' is the definition.
(order can mean a demand or instruction)
'called round on policeman's' is the wordplay.
'called' becomes 'named' (synonyms).
'round' says the letters should be written backwards.
'on' is a charade indicator (letters next to each other).
'policeman' becomes 'ds' (abbreviation for Detective Sergeant).
'named' in reverse letter order is 'deman'.
(Other definitions for demands that I've seen before include "Insists upon" , "Requires" , "Insistent requests" , "Orders" , "Asks peremptorily" .)