London theatre element (9)
I believe the answer is:
palladium
I believe this is a double definition.
'london theatre' is the first definition.
(I've seen this before)
'element' is the second definition.
(palladium is a kind of element)
(Other definitions for palladium that I've seen before include "guarantee of protection" , "London variety theatre - element - safeguard" , "Theatre in London; rare metal" , "Misery at own condition" , "Metal element" .)