Abduct for ransom (6)
I believe the answer is:
kidnap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">abduct for ransom</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)