Apprentice takes to public transport with extreme ease (7)
I believe the answer is:
trainee
'apprentice' is the definition.
(someone undergoing training)
'to public transport with extreme ease' is the wordplay.
'to public transport' becomes 'train' (train is a kind of public transport).
'with' is a charade indicator (letters next to each other).
'extreme' means to remove the middle letters.
'ease' with its centre removed is 'ee'.
'train'+'ee'='TRAINEE'
'takes' acts as a link.
(Other definitions for trainee that I've seen before include "Person being taught" , "One learning a job" , "Apprentice" , "encountered bad weather in driving area" , "New recruit" .)