Some with a demon — possessed! (3)
I believe the answer is:
had
'possessed' is the definition.
(to have something is to possess it)
'some with a demon' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'HAD' is hidden in the letters of 'with a demon'.
(Other definitions for had that I've seen before include "kept" , "Owned in the past" , "Was in possession of" , "Did trick" , "Was bound to be - caught" .)