Eccentric new CIA apprehension is a health hazard (7,6)
I believe the answer is:
cardiac arrest
'is a health hazard' is the definition.
I can't judge whether this definition defines the answer.
'eccentric new cia apprehension' is the wordplay.
'eccentric' becomes 'card' (I've seen this before).
'new' is an anagram indicator.
'apprehension' becomes 'arrest' (synonyms).
'cia' anagrammed gives 'iac'.
'card'+'iac'+'arrest'='CARDIAC ARREST'
Can you help me to learn more?
(Another definition for cardiac arrest that I've seen is " Stoppage of the heart".)