Celebrity put back a new business (5,2)
I believe the answer is:
start up
'a new business' is the definition.
(I've seen this before)
'celebrity put back' is the wordplay.
'celebrity' becomes 'star' (a star is a celebrity or famous person).
'back' is a reversal indicator.
'put' back-to-front is 'tup'.
'star'+'tup'='START-UP'
(Other definitions for start up that I've seen before include "Action of initiating" , "New firm" , "Newly created business" , "Initiation" , "Beginning" .)