Cool person holds it, never flustered (5)
I believe the answer is:
nerve
'cool' is the definition.
(thesaurus)
'person holds it never flustered' is the wordplay.
'never' can be anagrammed to 'NERVE'.
However, I'm not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for nerve that I've seen before include "that may be attached to optic?" , "Cceek or courage" , "Impudence (colloq.)" , "Fearlessness" , "Cord that carries instructions from brain to body" .)