Poles more bitter after refusal guaranteed failure (10)
I believe the answer is:
nonstarter
'guaranteed failure' is the definition.
'nonstarter' can be an answer for 'failure' (synonyms). I am not certain of the 'guaranteed' bit.
'poles more bitter after refusal' is the wordplay.
'poles' becomes 'NS' (North and South poles).
'more bitter' becomes 'tarter' (I am not sure about this - if you are sure you should believe this answer much more).
'after' says to put letters next to each other.
'refusal' becomes 'no' (saying no to something).
'ns'+'tarter'='nstarter'
'nstarter' after 'no' is 'NONSTARTER'.
Can you help me to learn more?
(Other definitions for nonstarter that I've seen before include "One who doesn't even begin" , "Someone who is never going to succeed" , "Something with no chance of success" , "Unviable thing" , "unfeasible idea" .)