Turns on former partner with cocaine, sex and tablets (7)
I believe the answer is:
excites
'turns on' is the definition.
('excite' can be a synonym of 'turn on')
'former partner with cocaine sex and tablets' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'with' says to put letters next to each other.
'cocaine sex' becomes 'cit' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'tablets' becomes 'es' (E can refer to an ecstasy tablet).
'ex'+'cit'+'es'='EXCITES'
Can you help me to learn more?
(Other definitions for excites that I've seen before include "Makes eager" , "Provokes" , "Animates" , "Arouses feelings in" , "Kindles" .)