Laundress finally leaving wicked hypnotist (8)
I believe the answer is:
svengali
'hypnotist' is the definition.
(fictional hypnotist)
'laundress finally leaving wicked' is the wordplay.
'finally' suggests the final letters.
'wicked' indicates an anagram.
The final letter of 'laundress' is 's'.
'leaving' anagrammed gives 'vengali'.
's'+'vengali'='SVENGALI'
(Other definitions for svengali that I've seen before include "Sinister controller (of another person)" , "Leavings of a fictional evil hypnotist" , "Trilby's mesmerist" , "Person who tries to force another to do his bidding" , "Evil manager" .)