Seriously bring in new style (9)
I believe the answer is:
earnestly
'seriously' is the definition.
(I know that seriously can be written as earnestly)
'bring in new style' is the wordplay.
'bring in' becomes 'earn' (as in bringing in money).
'new' is an anagram indicator.
'style' anagrammed gives 'estly'.
'earn'+'estly'='EARNESTLY'
(Other definitions for earnestly that I've seen before include "with heart and soul" , "Showing serious intent" , "Relent, say, in sincere and serious manner" , "In all seriousness" , "Showing commitment" .)