Abduct for ransom (6)
I believe the answer is:
kidnap
'abduct for ransom' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for kidnap that I've seen before include "Abduct (a person)" , "Seize, usually for ransom" , "'Abduct, snatch (6)'" , "Small island" , "Take as hostage" .)