Those who take drugs giving rise to research in America (5)
I believe the answer is:
users
'those who take drugs' is the definition.
(I know this)
'rise to research in america' is the wordplay.
'rise' shows that the letters should be reversed in order.
'to research' becomes 'res' (academic abbreviation).
'in' means one lot of letters goes inside another.
'america' becomes 'US' (United States).
'res' back-to-front is 'ser'.
'ser' inserted into 'us' is 'USERS'.
'giving' is the link.
(Other definitions for users that I've seen before include "Ruses for employers" , "Drug addicts" , "Operators" , "People who take drugs" , "Drug takers" .)