Ramp upsetting pushchair (4)
I believe the answer is:
pram
'pushchair' is the definition.
(synonyms)
'ramp upsetting' is the wordplay.
'upsetting' indicates anagramming the letters.
'ramp' anagrammed gives 'PRAM'.
(Other definitions for pram that I've seen before include "early transport" , "Baby transporter" , "Baby's carriage" , "Nanny may use this" , "Baby's wheels" .)