A refusal before America shows common sense (4)
I believe the answer is:
nous
'common sense' is the definition.
(nous is a kind of common sense)
'a refusal before america' is the wordplay.
'a refusal' becomes 'no'.
'before' says to put letters next to each other.
'america' becomes 'us' (abbreviation for the United States).
'no'+'us'='NOUS'
'shows' is the link.
(Other definitions for nous that I've seen before include "FT in Paris, say" , "How the French describe their own" , "we recognised in Nancy" , "Informal common sense" , "we found in Sorbonne, for example" .)