Spiritual leader leaving out powerful influencer (8)
I believe the answer is:
svengali
'powerful influencer' is the definition.
(fictional hypnotist)
'spiritual leader leaving out' is the wordplay.
'leader' indicates taking the first letters.
'out' is an anagram indicator (out can mean wrong or inaccurate).
The first letter of 'spiritual' is 's'.
'leaving' anagrammed gives 'vengali'.
's'+'vengali'='SVENGALI'
(Other definitions for svengali that I've seen before include "George du Maurier character who controls Trilby" , "George du Maurier's controlling character" , "Trilby's mesmerist" , "Evil person - leavings (anag)" , "One exerting evil mental control over another" .)