Trainee I’d met - confused between extremes (12)
I believe the answer is:
intermediate
'between extremes' is the definition.
(I've seen this before)
'trainee i'd met confused' is the wordplay.
'confused' is an anagram indicator.
'trainee'+'id'+'met'='traineeidmet'
'traineeidmet' with letters rearranged gives 'INTERMEDIATE'.
(Other definitions for intermediate that I've seen before include "Coming between (eg, in size)" , "Act as agent" , "Coming between two things in some way" , "Lying between two extremes" .)