Five torpedoes where room built for blade-on-blade machine (5,5)

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

An envelope (‘torpedoes’) of V (Roman numeral, ‘five’) in HOERMOWER, an anagram (‘built’) of ‘where room’, with a cryptic definition in which the first ‘blade’ is a cutter, and the second, grass.