Selection.Text returns the current selection's text.
In principle, the syntax for your Replace command is:
Selection.Find.ClearFormatting
Selection.Find.Replacement.ClearFormatting
With Selection.Find
.Text = Selection.Text
.Replacement.Text = ""
.Forward = True
.Wrap = wdFindContinue
.Format = False
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
End With
Selection.Find.Execute Replace:=wdReplaceAll
You replace by an empty string, thus delete every instance of the text to find.
But: You have to decide of course how to handle the formatting of the selected text, maybe have to analyze your selected block first because replacing might not work with control chars neglected by Selection.Text ... This is just the start, you need to specify what you want and then ask again, yourself or us. Meanwhile Record macro and the word vba reference are your friends.