Force of spirit exorcist initially left behind (5)
I believe the answer is:
impel
'force' is the definition.
(I know that force can be written as impel)
'spirit exorcist initially left behind' is the wordplay.
'spirit' becomes 'imp' (I have seen 'Evil spirit ' mean 'imp' so perhaps 'spirit' could also mean 'imp').
'initially' suggests taking the first letters.
'left' becomes 'l' (common abbreviation).
'behind' says to put letters next to each other.
The initial letter of 'exorcist' is 'e'.
'imp'+'e'+'l'='IMPEL'
'of' is the link.
(Other definitions for impel that I've seen before include "Drive or coerce" , "Spur on" , "Urge or propel" , "Urge or drive to do something" , "Force forwards" .)