Celebrate former auction item turning up (5)
I believe the answer is:
extol
'celebrate' is the definition.
(I've seen this before)
'former auction item turning up' is the wordplay.
'former' becomes 'ex'.
'auction item' becomes 'lot' (I've seen this before).
'turning up' says the letters should be written in reverse.
'lot' reversed gives 'tol'.
'ex'+'tol'='EXTOL'
(Other definitions for extol that I've seen before include "trumpet" , "Glorify - honour" , "be lavish with praise" , "Highly commend" , "Laud; glorify" .)