He raises unnecessary fears of a mistral storm (8)
I believe the answer is:
alarmist
'he raises unnecessary fears' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a mistral storm' is the wordplay.
'storm' indicates an anagram.
'mistral' anagrammed gives 'larmist'.
'a'+'larmist'='ALARMIST'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for alarmist that I've seen before include "Creating needless worry" , "I magnify dangers" , "One spreads unnecessary worry or fear" , "spreading fear" , "Given to causing unnecessary panic" .)