Drug addict from America to fear, oddly (4)
I believe the answer is:
user
'drug addict' is the definition.
(thesaurus)
'america to fear oddly' is the wordplay.
'america' becomes 'us' (abbreviation for the United States).
'oddly' indicates alternate letters.
The alternating letters of 'fear' are 'er'.
'us'+'er'='USER'
'from' acts as a link.
(Other definitions for user that I've seen before include "Manipulative woman" , "With 1a [NEW] he'll need different login" , "Right long-established" , "Utiliser" , "Patron" .)