Impresario after concert books Queen (8)
I believe the answer is:
promoter
'impresario' is the definition.
(I know that impresario can be written as promoter)
'after concert books queen' is the wordplay.
'after' says to put letters next to each other.
'concert' becomes 'prom' (abbreviation for promenade concert).
'books' becomes 'OT' (abbreviation for Old Testament).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'prom' put next to 'ot' is 'promot'.
'promot'+'er'='PROMOTER'
(Other definitions for promoter that I've seen before include "Person seeking financial support" , "Sponsor" , "One pushing" , "One books entertainments" , "One putting on a sporting event" .)