Root of foreign affairs' west facing perspective (4)
I believe the answer is:
fang
'facing perspective' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'root of foreign affairs' west' is the wordplay.
'root of' suggests taking the first letters.
'affairs' west' becomes 'ang' (I can't justify this - if you can you should give a lot more credence to this answer).
The first letter of 'foreign' is 'f'.
'f'+'ang'='FANG'
Can you help me to learn more?
(Other definitions for fang that I've seen before include "'Large, sharp tooth (4)'" , "Large canine tooth" , "Wolf's tooth" , "Long pointed tooth" , "Large pointed tooth" .)