Heard nicked criminal on trial here? (5)
I believe the answer is:
court
'criminal on trial here?' is the definition.
(where a criminal stands trial)
'heard nicked' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'nicked' becomes 'caught' (nick can mean to catch or apprehend).
'caught' is a homophone of 'COURT'.
(Other definitions for court that I've seen before include "Woo, quadrangle" , "Attempt to gain" , "Pay suit to, woo" , "Where trials take place" , "Judicial body" .)