Letter before Zulu (6)
I believe the answer is:
yankee
'letter before zulu' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for yankee that I've seen before include "American (loosely)" , "Radio codeword for Y" , "A bet on several horses at once - US citizen" , "US northerner to a southerner" , "one who's pulled?" .)