Word before "Nevada" or "Leone" (6)
I believe the answer is:
sierra
'word before nevada or leone' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sierra that I've seen before include "Jagged mountains - code word for S" , "that Romeo is not after" , "Mountain chain, S (radio comms.)" , "letter read out on the radio" , "- Nevada, Spanish mountain range" .)