Clue: Writer's covering President endlessly, as before (6)
Answer: IBIDEM
Explanation: Definition: as before
 I'M("I am"/contraction of "writer is", with the writer self-referentially using the first person pronoun) **containing**(covering) "Biden"(currently President of the USA) ***minus its last letter***(endlessly).
Defn: …/in the same place, in Latin.