Red parts of one's arms (5)
I believe the answer is:
gules
This clue might be a double definition.
'red' is the first definition.
(I know that gules is a type of red)
'parts of one's arms' is the second definition.
'gules' can be an answer for 'arms' (thesaurus). I'm not sure about the 'parts of one's' bit.
Can you help me to learn more?
(Other definitions for gules that I've seen before include "Heraldic red" , "heraldic colour" , "Red tincture" , "Red, in heraldry" .)