Solid property in Brazilian currency, extremely tidy sum! (6)
I believe the answer is:
realty
'solid property' is the definition.
'realty' can be an answer for 'property' (realty is a kind of property). I'm not certain of the 'solid' bit.
'brazilian currency extremely tidy sum' is the wordplay.
'brazilian currency' becomes 'real' (I've seen this before).
'extremely tidy sum' becomes 'ty' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'real'+'ty'='REALTY'
'in' is the link.
Can you help me to learn more?
(Other definitions for realty that I've seen before include "Property legally" , "Property ownership in the US" , "American real estate" , "Immovable property" , "Lyrate (anag.)" .)