Warning about the auction (7)
I believe the answer is:
caution
'warning' is the definition.
(I know that caution is a type of warning)
'about the auction' is the wordplay.
'about' indicates anagramming the letters.
'auction' is an anagram of 'CAUTION'.
(Other definitions for caution that I've seen before include "Admonish - warning" , "Care taken to avoid danger" , "Warn strongly" , "Heed - warning - funny person" , "amusing type" .)