Private trains or planes (8)
I believe the answer is:
personal
'private' is the definition.
('personal' is associated in meaning with 'private')
'trains or planes' is the wordplay.
'trains' indicates anagramming the letters (I've seen 'train' mean this (to train can mean to grow something into a shape)).
'or'+'planes'='orplanes'
'orplanes' with letters rearranged gives 'PERSONAL'.
(Other definitions for personal that I've seen before include "Offensively intrusive" , "Private - bodily" , "Relating to the individual" , "Applied to a particular individual" , "Confidential" .)