Malone. I also wondered if it was just GUNS, which would be faithful to the poem. If so, this would give us seven cells for the crosses. This only works if we ignore the central one. Maybe that one is just there to act as some sort of definition/indicator? But, personally, l am not convinced.
Also wonder about "appropriate colours". What colour are the singers? Ditto the weapons. Or, if they are to be highlighted, the crosses?
Cockle, l now see those singers in the RH down column.
This sort of thing seems to often happen in lnq puzzles.