Magic Circle: sect must include foremost of conjurors (6)
I believe the answer is:
occult
'magic' is the definition.
(thesaurus)
'circle sect must include foremost of conjurors' is the wordplay.
'circle' becomes 'o'.
'sect' becomes 'cult' (I've seen this in other clues).
'must include' means one lot of letters goes inside another.
'foremost of' suggests taking the first letters.
The initial letter of 'conjurors' is 'c'.
'cult' enclosing 'c' is 'ccult'.
'o'+'ccult'='OCCULT'
(Other definitions for occult that I've seen before include "Involving supernatural phenomena" , "Supernatural practices" , "Involving magical powers" , "Involving the supernatural, esoteric" , "Mystical, involving the supernatural" .)