A number will resign; that’s clear (6)
I believe the answer is:
acquit
'clear' is the definition.
(I know that clear can be written as acquit)
'a number will resign' is the wordplay.
'a number will' becomes 'ac' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'resign' becomes 'quit' (to quit something is to resign from it).
'ac'+'quit'='ACQUIT'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for acquit that I've seen before include "Free - act" , "Absolve" , "Declare to be innocent in court" , "Discharge from court as innocent" , "Discharge as innocent, dismiss charge" .)