Copy European drug smuggler importing a source of this (7)
I believe the answer is:
Here is my best explanation:
'copy' is the definition.
('emulate' can be a synonym of 'copy')
'european drug smuggler importing a source of this' is the subsidiary indication.
'european' becomes 'e' (abbreviation e.g. EU).
'drug smuggler' becomes 'mule' (I've seen this in other clues).
'importing' indicates putting letters inside.
'source of' indicates taking the first letters.
The first letter of 'this' is 't'.
'mule' enclosing 'at' is 'mulate'.
(Other definitions for emulate that I've seen before include "Try to do as well as another", "Copy - rival", "Follow in the footsteps of", "Copy -- reach equality with", "Attempt to match", "Follow suit", "Mimic", "Try to equal or surpass (someone)", "Strive to equal or match" and "Strive to equal or surpass".)