Thinking lead role in Asia will be seized by some form of Oriental (9)
I believe the answer is:
rationale
'thinking' is the definition.
(rationale is a kind of thinking)
'be seized by some form of oriental' is the wordplay.
'be' becomes 'rate' (rating is a kind of being).
'seized by' means one lot of letters goes inside another.
'some form of oriental' becomes 'ional' (I can't explain this - if you can you should give a lot more credence to this answer).
'rate' enclosing 'ional' is 'RATIONALE'.
'lead role in asia will' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for rationale that I've seen before include "Underlying principle" , "Motivation" , "Logical reason for action" , "Logic, reasoning" , "explanation" .)