Fellow finds a trainee majestic (5)
I believe the answer is:
royal
'majestic' is the definition.
(I know that majestic can be written as royal)
'fellow finds a trainee' is the wordplay.
'fellow' becomes 'roy' (man's name).
'finds' means one lot of letters go next to another.
'trainee' becomes 'l'.
'roy'+'a'+'l'='ROYAL'
(Other definitions for royal that I've seen before include "Relating to kings/queens" , "Befitting a monarch" , "Relating to a sovereign" , "- blue; - assent" , "Splendid!" .)