Friend having no right to be a devil! (5)
I believe the answer is:
fiend
'a devil' is the definition.
('fiend' can be a synonym of 'devil')
'friend having no right' is the wordplay.
'having no' is a deletion indicator.
'right' becomes 'r' (common abbreviation).
'friend' with 'r' removed is 'FIEND'.
'to be' acts as a link.
(Other definitions for fiend that I've seen before include "addict" , "monster" , "Devilish person" , "Demon, ogre" , "Evil supernatural being" .)