I am likely to be out of the question (10)
I believe the answer is:
impossible
'be out of the question' is the definition.
(synonyms)
'i am likely' is the wordplay.
'i am' becomes 'I'm' (contraction).
'likely' becomes 'possible' (associated in meaning).
'im'+'possible'='IMPOSSIBLE'
'to' acts as a link.
(Other definitions for impossible that I've seen before include "some kind of mission" , "Not able to take place" , "Not able to exist" , "See 10" , "See 14 down" .)