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 can't see how they can define each other.
'root of foreign affairs' west' is the wordplay.
'root of' says to take the initial letters.
'affairs' west' becomes 'ang' (I can't explain this - if you can you should give a lot more credence to this answer).
The initial 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" .)