Study includes California, Germany and Middle Eastern type that's corrupt (8)
I believe the answer is:
decadent
'corrupt' is the definition.
(thesaurus)
'study includes california germany and middle eastern' is the wordplay.
'study' becomes 'den' (I've seen this before).
'includes' means one lot of letters goes inside another.
'california germany' becomes 'cade' (I can't justify this - if you can you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'middle' means to look at the middle letters.
The middle of 'eastern' is 't'.
'den' enclosing 'cade' is 'decaden'.
'decaden'+'t'='DECADENT'
'type that's' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for decadent that I've seen before include "Luxuriously self-indulgent" , "abandoned" , "Morally corrupt" , "Rotten" , "Culturally in decline" .)