One no longer able to make changes could make one spit (4,6)
I believe the answer is:
dead ringer
'longer able to make changes could make one spit' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'one no' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'no' could be 'n' (common abbreviation) and 'n' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dead ringer that I've seen before include "One can do no more changes!" , "that might explain silent phone call?" , "Lookalike" , "Exact image" , "one looks very much like another" .)