Provide incentive for singer sadly involved in drugs (8)
I believe the answer is:
energise
'provide incentive' is the definition.
(energise can mean to incentivise or motivate)
'singer sadly involved in drugs' is the wordplay.
'sadly' indicates an anagram.
'involved in' is an insertion indicator.
'drugs' becomes 'ee' (two E's - E can mean ecstasy).
'singer' anagrammed gives 'nergis'.
'nergis' inserted inside 'ee' is 'ENERGISE'.
'for' acts as a link.
(Other definitions for energise that I've seen before include "Activate" , "To banish inertia" , "Give active force" , "give vigour" , "Give power to" .)