The Devil (5)
'the devil' is the definition.
('Satan' can be a synonym of 'devil')
This is all the clue.
(Other definitions for satan that I've seen before include "Prince of Darkness" , "Fallen archangel" , "Diabolical figure" , "arch-fiend" , "The devil, Beelzebub" .)
'the devil' is the definition.
(synonyms)
This is all the clue.
(Other definitions for demon that I've seen before include "Evildoer" , "Wizard" , "Fiend, devil" , "Ghoul" , "malignant spirit" .)
'the devil' is the definition.
('Old Nick' can be a synonym of 'devil')
This is all the clue.
(Other definitions for old nick that I've seen before include "Scratch" , "Newgate's" , "The aged devil" , "spirit of evil" , "'The prince of darkness (3,4)'" .)
'the devil' is the definition.
(Lucifer is a name for the devil)
This is the entire clue.
(Other definitions for lucifer that I've seen before include "once a match for > Dickens" , "Devilish sort of match" , "Beelzebub, Old Nick" , "Devil - match!" , "leader of rebellion" .)
'the devil' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for old harry that I've seen before include "The Devil" , "Evil character" .)
'the devil' is the definition.
(I have seen 'Senior devil' mean 'mephistopheles' so perhaps 'devil' could also mean 'mephistopheles')
This is all the clue.
(Other definitions for mephistopheles that I've seen before include "diabolical character" , "Evil demon (Faust)" , "evil character" , "Buyer of Faust's soul" , "Senior devil" .)