Entertaining American male on drugs (7)
I believe the answer is:
amusing
'entertaining' is the definition.
(similar in meaning)
'american male on drugs' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'male' becomes 'm' (common abbreviation).
'on drugs' becomes 'using' (I've seen this in another clue).
'a'+'m'+'using'='AMUSING'
(Other definitions for amusing that I've seen before include "Causing a smile" , "Humorous" , "Pleasantly entertaining" , "Entertaining, diverting" , "might be funny" .)