Criminal prepared to kidnap queen (7)
I believe the answer is:
crooked
'criminal' is the definition.
(I've seen this before)
'prepared to kidnap queen' is the wordplay.
'prepared' becomes 'cooked' (as in cooking the books).
'to kidnap' means one lot of letters goes inside another (inserted letters are kidnapped or taken).
'queen' becomes 'r' (abbreviation for regina, e.g. in ER ).
'cooked' going around 'r' is 'CROOKED'.
(Other definitions for crooked that I've seen before include "Misshapen" , "Warped" , "Awry - untrustworthy" , "Criminal" , "Bent, twisted" .)