Carriage said to be well-proportioned (8)
I believe the answer is:
handsome
'be well-proportioned' is the definition.
(I've seen this before)
'carriage said' is the wordplay.
'carriage' becomes 'hansom' (hansom is a kind of carriage).
'said' shows a homophone (sound like).
'hansom' sounds like 'HANDSOME'.
'to' is the link.
(Other definitions for handsome that I've seen before include "large" , "Attractive, liberal" , "Goodly" , "beautiful" , "Good-looking or generous" .)