Get a dataset of an SQL query in Laravel

To retrieve an identifier from a table in order to be able to work it separately, the problem I have is that when I get it, the sql query gives it to me in the form of a table that I was not able to to convert to a chain.

Here is the code:

                                $ idClient = DB :: select ("SELECT id among clients WHERE nit = $ nit");

echo $ idClient;

the array will contain only one element, but it has not been able to convert it to a string, whereas it is only one element.
it comes to me as an error:
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I want to get this "id" of the query in string form, but I could not.