Big celebrity gets Mara excited (8)
I believe the answer is:
megastar
'big celebrity' is the definition.
'gets mara excited' is the wordplay.
'excited' indicates an anagram.
'gets'+'mara'='getsmara'
'getsmara' with letters rearranged gives 'MEGASTAR'.
(Other definitions for megastar that I've seen before include "Great Sam (anag)" , "Exceptionally famous man" , "famous entertainer" , "Dazzlingly successful person" , "A-list celeb" .)