Put out about boarding European aircraft (5)
I believe the answer is:
eject
'put out' is the definition.
(I've seen this before)
'about boarding european aircraft' is the wordplay.
'about' becomes 'c' (circa).
'boarding' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'aircraft' becomes 'jet' (jet is a kind of aircraft).
'e'+'jet'='ejet'
'c' going into 'ejet' is 'EJECT'.
(Other definitions for eject that I've seen before include "Oust" , "Send out forcibly" , "Bail out" , "Force out violently" , "Suddenly throw out" .)