Treats dog with drug and a bit of sympathy (5)
I believe the answer is:
cures
'treats' is the definition.
(as in medical treatment)
'dog with drug and a bit of sympathy' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'with' says to put letters next to each other.
'drug' becomes 'e' (E is another name for ecstasy).
'and' is a charade indicator (letters next to each other).
'a bit of' indicates taking the first letters.
The first letter of 'sympathy' is 's'.
'cur'+'e'+'s'='CURES'
(Other definitions for cures that I've seen before include "Makes better, heals" , "Remedies" .)