Navy tracking wayward marine who made unproven claims (7)

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

N{avy} after(=tracking) after marine*. I think the def refers to the Riemann hypothesis, which I won't attempt to explain as I haven't the foggiest what it's about, but it is one of the most important unproven conjectures in mathematics.