Good try!
However, you are forgetting the 'twilight' element. Also, it doesn't say that 'he' mingles with doom, but that 'twilight' does. The straight part of the clue doesn't usually contribute letters to the cryptic part; in general it kind of stands apart from it, so to speak.
It kinds of betrays the hobbitlike side of me that Turambar often makes me think of Carambars - candy bars that were always in the confectionery and cake shops when my parents started taking us to France for holidays. Probably not the effect Tolkien was going for at all.
