Fair guaranteed publicity (8)
I believe the answer is:
exposure
'publicity' is the definition.
(I've seen this before)
'fair guaranteed' is the wordplay.
'fair' becomes 'expo' (an expo is a type of large exhibition).
'guaranteed' becomes 'sure' (I've seen this in other clues).
'expo'+'sure'='EXPOSURE'
(Other definitions for exposure that I've seen before include "Lack of shelter" , "illness caused by cold" , "Use of flash" , "Lack of cover" , "Risk for Antarctic explorer" .)