Cool courage is never shattered (5)
I believe the answer is:
nerve
'cool courage' is the definition.
(I've seen this before)
'never shattered' is the wordplay.
'shattered' is an anagram indicator.
'never' anagrammed gives 'NERVE'.
'is' is the link.
(Other definitions for nerve that I've seen before include "Grit" , "Sensation transmitter" , "Confidence" , "Intrepidity" , "Strand of body tissue" .)