Old Bob manipulated leaving sinister controller (8)
I believe the answer is:
svengali
'sinister controller' is the definition.
(I've seen this before)
'old bob manipulated leaving' is the wordplay.
'old bob' becomes 's' (abbreviation for bob or shilling used before 1971).
'manipulated' is an anagram indicator.
'leaving' anagrammed gives 'vengali'.
's'+'vengali'='SVENGALI'
(Other definitions for svengali that I've seen before include "(controlling person)" , "Sinister manipulator" , "George du Maurier character who controls Trilby" , "Leavings of a fictional evil hypnotist" , "man of influence" .)