Video game created by American on drugs (9)
I believe the answer is:
asteroids
'video game' is the definition.
(classic video game)
'american on drugs' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'on' is a charade indicator (letters next to each other).
'drugs' becomes 'steroids' (steroid is a type of drug).
'a'+'steroids'='ASTEROIDS'
'created by' acts as a link.
(Other definitions for asteroids that I've seen before include "Small planets orbiting the sun" , "Heavenly bodies" , "Do satires address small planets?" , "lumps of rock" , "Small celestial bodies that move around the sun" .)