Aunt over, spreading gold in style (3,7)
I believe the answer is:
art nouveau
'style' is the definition.
(I've seen this before)
'aunt over spreading gold' is the wordplay.
'spreading' indicates an anagram.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'aunt'+'over'='auntover'
'auntover' anagrammed gives 'artnouve'.
'artnouve'+'au'='ART NOUVEAU'
'in' acts as a link.
(Other definitions for art nouveau that I've seen before include "design movement" , "1890s' French style" , "1890s design style" , "Architectural style of the 1890s" , "no longer in style" .)