One again shows anger (3)
I believe the answer is:
ire
'anger' is the definition.
(ire is intense rage)
'one again' is the wordplay.
'one' becomes 'i' (Roman numeral).
'again' becomes 're' (prefix meaning 'again').
'i'+'re'='IRE'
'shows' acts as a link.
(Other definitions for ire that I've seen before include "exasperation" , "heat" , "Irritation, anger" , "Paddy" , "Displeasure" .)