Teacher makes a mess of trout (5)
I believe the answer is:
tutor
'teacher' is the definition.
(I know that tutor is a type of teacher)
'a mess of trout' is the wordplay.
'a mess of' indicates anagramming the letters (I've seen 'a mess' mean this).
'trout' with letters rearranged gives 'TUTOR'.
'makes' is the link.
(Other definitions for tutor that I've seen before include "class leader" , "Private instructor" , "Master" , "Give individual instruction" , "Trout (anag)" .)