Inattentive knight wild beast devours (6)
I believe the answer is:
absent
'inattentive' is the definition.
(similar in meaning)
'knight wild beast devours' is the wordplay.
'knight' becomes 'N' (chess abbreviation).
'wild' indicates an anagram.
'devours' indicates putting letters inside (inserted letters are devoured).
'beast' anagrammed gives 'abset'.
'n' put inside 'abset' is 'ABSENT'.
(Other definitions for absent that I've seen before include "Missing or dreamy" , "Not attending" , "AWOL" , "nowhere to be seen" , "Not where one should be" .)