In a way, an odd thing to find in one's blood? (5)
I believe the answer is:
serum
'in one's blood?' is the definition.
'serum' can be an answer for 'blood?' (thesaurus). I'm not sure about the 'in one's' bit.
'in a way an odd thing' is the wordplay.
'in' means one lot of letters goes inside another.
'a way' becomes 's' (Compass direction - South).
'an odd' becomes 'rum' (rum can mean strange or dubious).
'thing' becomes 'e' (I can't justify this - if you can you should give a lot more credence to this answer).
's'+'rum'='srum'
'srum' going around 'e' is 'SERUM'.
'to find' is the link.
Can you help me to learn more?
(Other definitions for serum that I've seen before include "potential shot in the arm?" , "Muser in blood" , "Constituent of blood" , "Antitoxin derived from blood" , "Antidote" .)