If your [Contractor] table has as its primary field a name-string that matches the one being imported, then, yes: Define that field as a linked-record field pointing to [Contractor]. Airtable will convert strings imported into that field as a link to an existing record of that name; if no matching string is found, it will create a new [Contractor] record.
The only caveat (well, main caveat) is that you can only import a single linked record. That is to say, while you could copy-and-paste ‘Record1, Record2’ into a linked-record field and have Airtable create a link to ‘Record1’ and a link to ‘Record2’, if you import that value, Airtable will create a link to a single record whose primary field is ‘Record1, Record2’.
Actually, now I think about it, this reply comes with its own caveat: Namely, I have not tested this using the Import CSV Block since that block was modified to update, rather than replace, existing records. There is a possibility its behavior has changed.
