Whether the "Description" column is a multiple lines of text column?
1.Edit page -> Add a script editor web part -> Add below codes into the script editor web part.
<style>
.ms-vh-div[DisplayName='Description']
{
width : 3000px !important;
}
</style>
2.Edit page -> Add a content editor web part -> Add below codes in the txt file into the content editor web part.
95130-code.txt
3.Result.

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