Urge wards to bring a prosecution (5,7)
I believe the answer is:
press charges
'bring a prosecution' is the definition.
(prosecute someone in court)
'urge wards' is the wordplay.
'urge' becomes 'press' (synonyms).
'wards' becomes 'charges' (both can mean children under one's care).
'press'+'charges'='PRESS CHARGES'
'to' acts as a link.
(Other definitions for press charges that I've seen before include "prosecute" , "to take legal action?" , "Intend taking action" .)