Trainee nurse picked up by boss on time (7)
I believe the answer is:
student
'trainee' is the definition.
(a student is in training)
'nurse picked up by boss on time' is the wordplay.
'nurse' becomes 'en' (abbreviation for enrolled nurse).
'picked up by' is an insertion indicator (some letters collected or picked up by others).
'boss' becomes 'stud' (both can mean a metal decoration).
'on' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'stud'+'t'='studt'
'en' placed within 'studt' is 'STUDENT'.
(Other definitions for student that I've seen before include "University attendee" , "One at university" , "A learner as at school" , "Scholar" , "Maybe fresher" .)