German city starts to treat immigrants as legally required (9)
I believe the answer is:
essential
'required' is the definition.
(thesaurus)
'german city starts to treat immigrants as legally' is the wordplay.
'german city' becomes 'essen' (I've seen this before).
'starts to' says to take the initial letters.
The first letters of 'treat immigrants as legally' is 'tial'.
'essen'+'tial'='ESSENTIAL'
(Other definitions for essential that I've seen before include "Key" , "organic" , "Indispensable, necessary" , "must-have item" , "Basic or necessary" .)