Blitz auction held outside hotel (5)
I believe the answer is:
shell
'blitz' is the definition.
(thesaurus)
'auction held outside hotel' is the wordplay.
'auction' becomes 'sell' ().
'held outside' indicates putting letters inside.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'sell' going around 'h' is 'SHELL'.
(Other definitions for shell that I've seen before include "Protective outer case" , "Characteristic feature of crustacean" , "Tortoise's home" , "(Turtle's) carapace" , "multinational?" .)