Son kidnapped by a criminal is not here (6)
I believe the answer is:
absent
'is not here' is the definition.
(absent from this place)
'son kidnapped by a criminal' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'kidnapped by' indicates putting letters inside.
'criminal' becomes 'bent' (bent can mean corrupt or criminal).
'a'+'bent'='abent'
's' placed within 'abent' is 'ABSENT'.
(Other definitions for absent that I've seen before include "AWOL" , "Missing or dreamy" , "Missing, lacking" , "Not attending" , "Not at a specified place" .)