Expose whitewash at the United Nations? (7)
I believe the answer is:
uncover
'expose' is the definition.
(I know that expose can be written as uncover)
'whitewash at the united nations?' is the wordplay.
'whitewash' becomes 'cover' (synonyms).
'at' means one lot of letters go next to another (I've seen this in other clues).
'the united nations?' becomes 'UN' (abbreviation).
'cover' after 'un' is 'UNCOVER'.
(Other definitions for uncover that I've seen before include "Make visible" , "bare" , "Expose, reveal" , "show?" , "Take the lid off" .)