Dismiss European high-flier that's taken cocaine (5)
I believe the answer is:
eject
'dismiss' is the definition.
(thesaurus)
'european high-flier that's taken cocaine' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'high flier' becomes 'jet' (I can't justify this - if you can you should give a lot more credence to this answer).
'that's taken' is an insertion indicator.
'cocaine' becomes 'c' (drugs abbreviation).
'jet' placed around 'c' is 'ject'.
'e'+'ject'='EJECT'
Can you help me to learn more?
(Other definitions for eject that I've seen before include "Put out or expel" , "Turf out" , "Throw out violently" , "Finally leave plane" , "Expel, chuck out" .)