Being twisted, I'll abase Catholic monarch (8)
I believe the answer is:
isabella
'catholic monarch' is the definition.
'isabella' can be an answer for 'monarch' (I have seen 'Spanish Queen ' mean 'isabella' so perhaps 'queen' could also mean 'isabella'). I am not sure about the 'catholic' bit.
'being twisted i'll abase' is the wordplay.
'being twisted' indicates an anagram.
'ill'+'abase'='illabase'
'illabase' anagrammed gives 'ISABELLA'.
Can you help me to learn more?
(Other definitions for isabella that I've seen before include "Wife of Ferdinand II of Aragon" , "Woman" , "Bails Lea out for the name" , "Consort of Edward II" , "drab colour" .)