Wagon in Ayr rolled over (5)
I believe the answer is:
lorry
'wagon' is the definition.
(I know that lorry is a type of wagon)
'in ayr rolled over' is the wordplay.
'in' indicates a hidden word.
'over' shows that the letters should be reversed in order.
'yrrol' is hidden within 'ayr rolled'.
'yrrol' back-to-front is 'LORRY'.
(Other definitions for lorry that I've seen before include "Load-carrying vehicle" , "Heavy goods vehicle" , "Commercial vehicle" , "From which stolen goods fall?" , "Industrial vehicle" .)