Auction item with American sports car (5)
I believe the answer is:
lotus
'sports car' is the definition.
(I've seen this before)
'auction item with american' is the wordplay.
'auction item' becomes 'lot' (a lot is an item for sale at auction).
'with' means one lot of letters go next to another.
'american' becomes 'US' (abbreviation for United States).
'lot'+'us'='LOTUS'
(Other definitions for lotus that I've seen before include "One of the lilies" , "It helps with memory loss" , "Fruit of forgetfulness - water lily - car marque" , "Tropical water-lily" , "F1 team and car maker" .)