Rich soil in Sao Paulo? Amazing (4)
I believe the answer is:
loam
'rich soil' is the definition.
(I've seen this before)
'in sao paulo? amazing' is the wordplay.
'in' indicates a hidden word.
'LOAM' is hidden in the letters of 'sao paulo amazing'.
(Other definitions for loam that I've seen before include "A rich fertile soil" , "Rich soil, good for growing" , "Rich soil with decayed vegetable matter" , "Type of soil" , "Rich soil consisting of a mixture of sand, clay and decaying organic materials" .)