Revelations certain to be a part of trade fairs (9)
I believe the answer is:
exposures
'revelations' is the definition.
(I know this)
'be a part of trade fairs' is the wordplay.
'be a' becomes 'sure' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'part of' is an insertion indicator (part of the inside).
'trade fairs' becomes 'expos' (short for exposition, a large exhibition).
'sure' placed within 'expos' is 'EXPOSURES'.
'certain to' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for exposures that I've seen before include "Revelations (of scandals, etc)" , "Snaps" .)