In anger, one shows spirit! (6)
I believe the answer is:
wraith
'spirit' is the definition.
(I've seen this before)
'in anger one' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'anger' could be 'wrath' (wrath is a kind of anger) and 'wrath' is present in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'shows' acts as a link.
Can you help me to learn more?
(Other definitions for wraith that I've seen before include "Ghost-like apparition" , "Spook" , "Deathly apparition" , "Ghostly apparition" , "Making an emotional appeal" .)