Bring in expert, securing new eminence (10)
I believe the answer is:
importance
'eminence' is the definition.
(thesaurus)
'bring in expert securing new' is the wordplay.
'bring in' becomes 'import' (bring in to a country).
'expert' becomes 'ace' (ace can informally mean very good).
'securing' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'ace' going around 'n' is 'ance'.
'import'+'ance'='IMPORTANCE'
(Other definitions for importance that I've seen before include "Mark" , "weight" , "moment" , "Great significance" , "See 6" .)