Transport meant possibly to carry duke (6)
I believe the answer is:
tandem
'transport' is the definition.
(tandem is a kind of transport)
'meant possibly to carry duke' is the wordplay.
'possibly' indicates an anagram.
'to carry' is an insertion indicator.
'duke' becomes 'd' (abbreviation).
'meant' is an anagram of 'tanem'.
'tanem' going around 'd' is 'TANDEM'.
(Other definitions for tandem that I've seen before include "Bicycle for two riders" , "Two-person bike" , "Bicycle for two (plus)" , "it's not normally what one rides" , "One behind another, as on bicycle" .)