Seeing Red Army needs greyish red Y-fronts (5)
I believe the answer is:
angry
'seeing red' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for angry that I've seen before include "Vexed" , "Incensed" , "In a paddy" , "Inflamed" , "Cross" .)