Clue: Lady on rock, evermore lethally emitting intoning, primarily? (7)
Answer: LORELEI
Explanation: Lady on rock, evermore lethally emitting intoning, primarily? (7)
First letters ('primarily') of '**L**ady **O**n **R**ock **E**vermore **L**ethally **E**mitting **I**ntoning'. &lit, of course, but for my money one of the clumsier 'primarily' clues.