2661: Spectrum
The unclued lights, four of two words, two individually or six pairs bear a common feature. One of the words does double duty, and another appears in two forms. Ignore three accents in the completed grid. Across 1 Criminal having cheese biscuit that’s not bad (4-7) 7 Found in cage in tribunal (3) 13 You and I will get lost first with it becoming brighter than 39! (4-3) 16 G and S operas at hotel that’s amongst the greens (5) 17 Scottish challenge at the poultry farm, unendingly (6) 18 Scowl at cow?