Apprentice from Aintree messed up (7)
I believe the answer is:
trainee
'apprentice' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for trainee that I've seen before include "One learning a job" , "encountered bad weather in driving area" , "Aintree (anag.)" , "New recruit" , "Person under instruction" .)