Replace `field` in `table` with the first word of `field`:
Code:
Update `table` set `field`=SubString(`field`, 1, Locate(' ', `field`) - 1)
You might want to test this first. Eg, use a "Where" condition, so it only updates one row (Maybe where `field2`='somevalue'). You could also do a quick backup by exporting the table data into a text file, then saving it somewhere.
An even better solution would be a Test table that you try it on first.
That way, if the change isn't as expected, your data isn't corrupted.