It can be drawn in red (5)
I believe the answer is:
'drawn in red' is the definition.
The definition and answer can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'it can' is the wordplay.
I cannot really see how this works, but
'can' could be 'loo' (slang) and 'loo' is found within the answer.
This explanation may well be incorrect...
'be' acts as a link.
Can you help me to learn more?
(Other definitions for blood that I've seen before include "Fiery temperament" , "Male siblings -- sworn friends" , "Recorded and respected ancestry" , "Oxygen carrier" , "Kinship; temperament" .)