Overturned wagon in back garden (4)
I believe the answer is:
yard
'back garden' is the definition.
'yard' can be an answer for 'garden' (I have seen 'American garden' mean 'yard' so perhaps 'garden' could also mean 'yard'). I am not sure about the 'back' bit.
'overturned wagon' is the wordplay.
'overturned' is a reversal indicator.
'wagon' becomes 'dray' (dray is a kind of wagon).
'dray' written backwards gives 'YARD'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for yard that I've seen before include "Imperial unit of length" , "American garden" , "Earth" , "Unit of measure" , "Measure - enclosed space" .)