Related Clues:

• Governing, managed to conceal source of riches — it's invisible
• Find out about unusual forms sensitive to some radiation
• Poem on strange duke's taken in new light
• Hot objects radiate this
• Unusually rare find that's not normally visible
• Type of radiation just outside visible range
• Radiation popular chap revealed around Burlington House
• Radiation from heated objects
• Find out about unusual part of spectrum
• Find out about exceptional light source
• Find mutant absorbing uncommon radiation
• Unusual find full of seldom-encountered radiation
• Rare find (anag.)
• Woolly ran if colour's outside the visible spectrum
• Certain rays