Oddly mean bloodsuckers getting bad blood (6)
I believe the answer is:
malice
'bad blood' is the definition.
(bad blood can mean malicious or spiteful feelings)
'oddly mean bloodsuckers getting' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'bloodsuckers' becomes 'lice' (bloodsucking creatures).
'getting' is a charade indicator (letters next to each other).
The alternate letters of 'mean' are 'ma'.
'ma'+'lice'='MALICE'
(Other definitions for malice that I've seen before include "Bitterness" , "Wrongful intention" , "Ill will, a desire to harm others" , "Spite or spleen, perhaps aforethought" , "Spitefulness" .)