Trial clears officer in police force (6)
I believe the answer is:
stress
'trial' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stress that I've seen before include "why off work?" , "Underline - tension" , "State mental or emotional strain" , "Lay emphasis on - it's a strain" , "Tension, pressure" .)