In eight clues, cryptic -indications omit reference to parts of answers; these parts must be highlighted, to reveal two words. Two unclued lights are definitions of the first word; the second word defines each of six unclued lights.

Across

11    Mineral, concrete and stone around (7)
12    Insane broadcast in colour (6)
16    Game with electronic ray (5)
19    Mass of plants, say, scattered around lake (7)
23    Flag outside shelter reflected in metal articles (7)
24    Tree in Durham landscape (4)
30    Being about to break even (7)
31    Greek poet endlessly effective (4)
32    Gong following noble part of organ (7)
34    Seaweed around stern (4)
35    Area behind...