Zulu area in severe danger (6)
I believe the answer is:
hazard
'danger' is the definition.
(hazard is a kind of danger)
'zulu area in severe' is the wordplay.
'zulu' becomes 'Z' (phonetic alphabet: alpha, bravo, charlie etc.).
'area' becomes 'a' (maths abbreviation).
'in' is an insertion indicator.
'severe' becomes 'hard' (synonyms).
'z'+'a'='za'
'za' going into 'hard' is 'HAZARD'.
(Other definitions for hazard that I've seen before include "Obstacle, source of danger" , "Risk; guess" , "Endanger, jeopardize" , "Potential danger" , "Danger; gamble" .)