It's a devil, we assume, holding them (5)

I believe the answer is:
demon
'it's a devil' is the definition.
('demon' can be a synonym of 'devil')
'assume holding them' is the wordplay.
'assume' becomes 'don' (I've seen this before).
'holding' means one lot of letters goes inside another.
'them' becomes 'em' ('em is an informal way of saying 'them').
'don' going around 'em' is 'DEMON'.
'we' is the link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for demon that I've seen before include "Evildoer" , "Genius" , "Ghoul" , "Fiend, devil" , "Fanatic; devil" .)
