Trout polluted coach (5)
I believe the answer is:
tutor
'coach' is the definition.
(synonyms)
'trout polluted' is the wordplay.
'polluted' is an anagram indicator.
'trout' is an anagram of 'TUTOR'.
(Other definitions for tutor that I've seen before include "Mentor" , "Private instructor" , "Master" , "Personal coach" , "Private educator" .)