Weir enjoyed an encouraging international debut, finishing 10th overall on the flat and fast 4km course in Chia, Sardinia.
Great Britain easily won the team event, with four runners finishing in the top 11.
For the second year running the race was won by Germany’s Konstanze Klosterhalfen, who clocked 12.26 minutes.
Second was Denmark’s Anna Emilie Moller, who finished in a time of 12.43 minutes, with Britain’s Harriet Knowles-Jones, who Weir beat at the trials on a different type of course in Liverpool, taking bronze in 12.52 minutes.
The next three British athletes all finished together. Amelia Quirk took ninth in 13.12, Weir was 10th in 13.16 and Gemma Holloway was 11th in 13.23.
Germany took second in the team event, with the Netherlands third, but they were both a long way behind Great Britain.