Get key from German city before it's returned by a student (9)
I believe the answer is:
essential
'get key' is the definition.
I can't tell whether this defines the answer.
'german city before it's returned by a student' is the wordplay.
'german city' becomes 'essen' (city in Germany).
'before' means one lot of letters go next to another.
'returned' is a reversal indicator.
'by' is a charade indicator (letters next to each other).
'student' becomes 'l' (as in L-plates for learner drivers).
'it' in reverse letter order is 'ti'.
'essen'+'ti'+'a'+'l'='ESSENTIAL'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for essential that I've seen before include "organic" , "Vital" , "as oil might be" , "Crucial" , "Key" .)