Be devious in taking the western line of approach (6)
I believe the answer is:
wangle
'be devious in' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'the western line of approach' is the wordplay.
'the western' becomes 'w'.
'line of approach' becomes 'angle' (I can't explain this - if you can you should believe this answer much more).
'w'+'angle'='WANGLE'
'taking' acts as a link.
Can you help me to learn more?
(Other definitions for wangle that I've seen before include "Accomplish something by scheming or trickery" , "Acquire by devious means" , "Obtain craftily" , "Get by crafty means" , "Obtain by being persuasive" .)