Turn to bigwig after being set up (5)
I believe the answer is:
pivot
'turn' is the definition.
(pivoting is a kind of turning)
'to bigwig after being set up' is the wordplay.
'bigwig' becomes 'VIP'.
'after' says to put letters next to each other.
'being set up' shows that the letters should be reversed in order.
'to'+'vip'='tovip'
'tovip' written backwards gives 'PIVOT'.
(Other definitions for pivot that I've seen before include "Turning pin" , "Centre point" , "Central point around which mechanism moves" , "Central point on which things turn" , "Revolve" .)