Abandon plane? No, lie back! (8)
I believe the answer is:
jettison
'abandon' is the definition.
(I've seen this before)
'plane? no lie back' is the wordplay.
'plane?' becomes 'jet' (jet plane).
'lie' becomes 'sit'.
'back' is a reversal indicator.
'no'+'sit'='nosit'
'nosit' back-to-front is 'tison'.
'jet'+'tison'='JETTISON'
(Other definitions for jettison that I've seen before include "Abandon, discard" , "Form of motor racing" , "Reject" , "Eject" , "Throw away (from ship or aeroplane?)" .)