… that rhymes with “convention”? I’m at a loss here.
I just ran it through the thesaurus option at http://www.dictionary.com and didn’t get any exact rhymes but got some close ones. You might want to have a look there.
How about “kleptoprehension?” I just made it up, and it seems etymologically OK.
illegal detention
Misappropriation
Misappropriation sounds about right, Finagle, except how it doesn’t exactly rhyme. Still the best bet so far, imho.
— G. Raven
confiscation
abduction (it sounds better if you have a really bad French accent)
illegal retention?
Liberation?
Depends on which side of the thieving you are on, I suppose.
We should ask the Cajun Man this question.
Direption - \Di*rep"tion, n. [L. direptio, fr. diripere to tear asunder, plunder; di- = dis- + rapere to seize and carry off.] The act of plundering, despoiling, or snatching away.
Try http://www.thesaurus.com/
Morrison’s Lament says,
and I agree. However, I thought appropriation a more accurate synonym than misappropriation so I checked. (Didn’t want to embarrass myself if it was a southern meaning!) :o Sure enough, in my thesaurus it lists appropriation as a synonym for theft. Some other possibilities are extortion and deprivation, neither of which seem like very good rhymes.
I kind of like the sound and cadence of ‘deprivation intention convention’ but it takes two words to get there instead of just one. 
Abby
no, not a poem. It’s a crossword puzzle with nine letters. The only letter supplied to me by another intersecting word is an “n” at the very end.
I was beginning to think it was a typing mistake, but “direption” fits. I’ll have to assume it’s the answer, because I sure couldn’t think of anything. Now to see what I win.
Thanks for your help, all. I’m still not entirely sure this wasn’t a typing mistake, but you guys found an answer anyways!
YAY! In your face, Cajun Man! 
Way to go Evilhanz! High five to ya. 
Abby
malintention
Nine letters, ending in “n?” try “violation” and see if it fits.