Satanic sort, very French, about to ensnare writer (7)
I believe the answer is:
serpent
'satanic sort' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'very french about to ensnare writer' is the wordplay.
'very french' becomes 'tres' ('very' in French).
'about' says the letters should be written backwards.
'to ensnare' means one lot of letters goes inside another.
'writer' becomes 'pen' (something which writes).
'tres' back-to-front is 'sert'.
'sert' enclosing 'pen' is 'SERPENT'.
Can you help me to learn more?
(Other definitions for serpent that I've seen before include "exhibit at zoo" , "Eve's tempter" , "Instrument of the past" , "Limbless reptile" , "Early wind instrument" .)