Nonsense written in columns exposing clowns (8)
I believe the answer is:
pierrots
'clowns' is the definition.
(I've seen this before)
'nonsense written in columns' is the wordplay.
'nonsense' becomes 'rot' (rot can mean nonsense or rubbish).
'written in' means one lot of letters goes inside another.
'columns' becomes 'piers' (I can't justify this - if you can you should give a lot more credence to this answer).
'rot' going within 'piers' is 'PIERROTS'.
'exposing' is the link.
Can you help me to learn more?
(Other definitions for pierrots that I've seen before include "Characters in French pantomime, usually dressed in white with whitened faces" , "Rips tore up the puppet clowns" .)