It can be drawn in red (5)
I believe the answer is:
'drawn in red' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'it can' is the wordplay.
I cannot quite understand how this works, but
'can' could be 'loo' (slang) and 'loo' is found in the answer.
This explanation may well be incorrect...
'be' is the 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" .)