Authority on courses in for training (11)
I believe the answer is:
connoisseur
'authority' is the definition.
(connoisseur is a kind of authority)
'on courses in for training' is the wordplay.
'for training' is an anagram indicator ('train' can mean to shape the growth of a plant).
'on'+'courses'+'in'='oncoursesin'
'oncoursesin' with letters rearranged gives 'CONNOISSEUR'.
(Other definitions for connoisseur that I've seen before include "discriminating judge" , "Knowledgeable art-lover" , "Expert judge of taste" .)