Reaction to jolt in non-upholstered carriage? (8)
I believe the answer is:
barouche
'carriage?' is the definition.
(barouche is a kind of carriage)
'reaction to jolt in non-upholstered' is the wordplay.
'reaction to jolt' becomes 'ouch' (exclamation of pain).
'in' is an insertion indicator.
'non-upholstered' becomes 'bare' (uncovered).
'ouch' put into 'bare' is 'BAROUCHE'.
(Other definitions for barouche that I've seen before include "Horse-drawn carriage - Cuba hero (anag)" , "Four-wheeled carriage" , "Victorian carriage" .)