Softest piece of cake in the West! (7)
I believe the answer is:
weakest
'softest' is the definition.
('weak' can be similar in meaning to 'soft')
'piece of cake in the west' is the wordplay.
'piece of cake' becomes 'ake' (I can't justify this - if you can you should believe this answer much more).
'in the' is an insertion indicator.
'ake' placed within 'west' is 'WEAKEST'.
Can you help me to learn more?
(Other definitions for weakest that I've seen before include "Having minimum power" , "Least strong" , "Least powerful" , "like some television links?" .)