I believe this is what you are looking for below, this will take a value from cell B1 and compare against values in Column A, and if the values are less than the value in B1, it will clear the contents of that cell:
Sub ClearLowerThan()
Dim c As Range, Rng As Range
Dim LastRow As Long
Dim ws As Worksheet: Set ws = Sheets("Sheet1")
'declare you worksheet, amend as required
LastRow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row
'get the last row with data on Column A
CompareVal = ws.Range("B1").Value
'get the value to compare against, in this case from cell B1
Set Rng = ws.Range("A1:A" & LastRow)
'set the range to compare against the value from B1
For Each c In Rng 'for each cell in the given range
If c.Value < CompareVal Then c.ClearContents
'if value of cell is less than the value to compare against, clear the cell contents.
Next
End Sub
solved Clear Excel Cell if Value less than another Cell value