Accept busy person embodies terrible evil (7)
I believe the answer is:
believe
'accept' is the definition.
(believing is a kind of accepting)
'busy person embodies terrible evil' is the wordplay.
'busy person' becomes 'bee' (I've seen this in other clues).
'embodies' means one lot of letters goes inside another.
'terrible' indicates an anagram.
'evil' with letters rearranged gives 'liev'.
'bee' enclosing 'liev' is 'BELIEVE'.
(Other definitions for believe that I've seen before include "Accept as true" , "Have faith; accept" , "Have faith; understand" , "Regard as true" , "Have confidence in" .)