Witness protects a suspect (9)
I believe the answer is:
spectator
'witness' is the definition.
('spectator' can be a synonym of 'witness')
'protects a suspect' is the wordplay.
'suspect' indicates an anagram.
'protects'+'a'='protectsa'
'protectsa' with letters rearranged gives 'SPECTATOR'.
(Other definitions for spectator that I've seen before include "fan" , "Onlooker at game" , "Eyewitness, viewer" , "found on the terraces?" , "One watching a game" .)