Magician in exhibition centre, one given to exaggeration (11)
I believe the answer is:
necromancer
'magician' is the definition.
('necromancer' can be a synonym of 'magician')
'exhibition centre one given to exaggeration' is the wordplay.
'exhibition centre' becomes 'nec' (National Exhibition Centre).
'one given to exaggeration' becomes 'romancer'.
'nec'+'romancer'='NECROMANCER'
'in' acts as a link.
(Other definitions for necromancer that I've seen before include "Sorcerer" , "magician" , "Black artist" , "Madame Arcati" .)