The writer supports not interrupting further rare mammal (9)
I believe the answer is:
monotreme
'rare mammal' is the definition.
'monotreme' can be an answer for 'mammal' (monotreme is a kind of mammal). I am not sure about the 'rare' bit.
'the writer supports not interrupting further' is the wordplay.
'the writer' becomes 'me' (the person who wrote the clues).
'supports' says to put letters next to each other (bottom letters provide a support for the top ones).
'interrupting' means one lot of letters goes inside another.
'further' becomes 'more' (synonyms).
'not' inserted into 'more' is 'monotre'.
'me' after 'monotre' is 'MONOTREME'.
Can you help me to learn more?
(Other definitions for monotreme that I've seen before include "Creature such as the platypus" , "Australian mammal" .)