Greek character on passenger vehicle carrying minute figure (7)
I believe the answer is:
rhombus
'figure' is the definition.
(rhombus is a kind of figure)
'greek character on passenger vehicle carrying minute' is the wordplay.
'greek character' becomes 'rho' (letter from the Greek alphabet**).
'on' says to put letters next to each other.
'passenger vehicle' becomes 'bus' (I've seen this before).
'carrying' means one lot of letters go next to another.
'minute' becomes 'm' (abbreviation).
'bus' after 'm' is 'mbus'.
'rho' next to 'mbus' is 'RHOMBUS'.
(Other definitions for rhombus that I've seen before include "Large bottle; vessel with spout" , "Equilateral parallelogram" , "Type of quadrilateral" , "Geometrical figure" , "Diamond-shaped figure" .)