Five imps are turning into blood-suckers (8)
I believe the answer is:
'blood-suckers' is the definition.
I can't tell whether this definition defines the answer.
'five imps are turning' is the wordplay.
'five' becomes 'V' (Roman numeral).
'turning' indicates anagramming the letters.
'impsare' anagrammed gives 'ampires'.
'into' acts as a link.
Can you help me to learn more?
(Other definitions for vampires that I've seen before include "Night owls" , "Dracula's people" , "Blood-suckers like Dracula" .)