Old form of transport leaving area, thus lying outside (9)
I believe the answer is:
extrinsic
'outside' is the definition.
(similar in meaning)
'old form of transport leaving area thus lying' is the wordplay.
I cannot quite see how this works, but
'old' could be 'ex' (prefix meaning former or onetime) and 'ex' is present in the answer.
'thus' could be 'sic' ('thus' in Latin) and 'sic' is located in the answer.
The remaining letters 'trin' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for extrinsic that I've seen before include "Not essential or inherent" , "What's inessential" , "Foreign" .)