Cutting edge of Romany XV? (4)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

CHI (X, Roman Greek letter ‘x’) + V. Devious conjoining of the Roman numerals. I knew ‘shiv’ as a blade from crosswords, and eventually stumbled into this. Reading Jackkt’s comment below, I’m inclined to agree. And thanks to Ulaca et al. for correcting my parsing.