Essentially disavowing presidency as invalid (4)
I believe the answer is:
void
'invalid' is the definition.
(similar in meaning)
'essentially disavowing presidency' is the wordplay.
'essentially' means to look at the middle letters.
'presidency' becomes 'id' (I can't explain this - if you can you should believe this answer much more).
The middle letters of 'disavowing' are 'vo'.
'vo'+'id'='VOID'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for void that I've seen before include "Free" , "Empty space or not legally binding" , "Null and empty" , "Null and invalid" , "Vacant; not valid" .)