Traveller departed without one carbon copy (9)
I believe the answer is:
replicate
'copy' is the definition.
(I've seen this before)
'traveller departed without one carbon' is the wordplay.
'traveller' becomes 'rep' (travel company worker).
'departed' becomes 'late' (late can mean deceased).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'one' becomes 'i' (Roman numeral).
'carbon' becomes 'C' (chemical symbol).
'i'+'c'='ic'
'late' going around 'ic' is 'licate'.
'rep'+'licate'='REPLICATE'
(Other definitions for replicate that I've seen before include "Make an exact copy of" , "Copy, reproduce" , "Copy exactly" .)