It's horrific to do this to the blood but around fifty will be healed. (6)
I believe the answer is:
curdle
'be healed' is the definition.
I can't tell whether this definition defines the answer.
'it's horrific to do this to the blood but around fifty' is the wordplay.
I cannot really understand how this works, but
'around' could be 'c' (abbreviation for 'circa') and 'c' is found within the answer.
'fifty' could be 'l' (Roman numeral) and 'l' is found within the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
The remaining letters 'urd' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'will' is the link.
Can you help me to learn more?
(Other definitions for curdle that I've seen before include "Of milk, go sour and form soft substance" , "Cause (milk) to coagulate" , "Go bad or sour" , "Of milk, turn sour and form thick substance" , "Go off like milk" .)