Rushed round island in support for apprentice (7)
I believe the answer is:
trainee
'apprentice' is the definition.
(someone undergoing training)
'rushed round island in support for' is the wordplay.
'rushed' becomes 'ran'.
'round' means one lot of letters goes inside another.
'island' becomes 'i'.
'in' indicates putting letters inside.
'support for' becomes 'tee' (I can't explain this - if you can you should believe this answer much more).
'ran' placed around 'i' is 'rain'.
'rain' going within 'tee' is 'TRAINEE'.
(Other definitions for trainee that I've seen before include "New recruit" , "Person being instructed in work" , "one needs to practice" , "Apprentice" , "encountered bad weather in driving area" .)