TIME FUNCTION

Alternatively, you could use VBA.

This version:

• updates every second,
• stops cleanly when closing the workbook,
• avoids duplicate timers if you accidentally run StartClock twice.

Standard Module (Insert → Module):

Option Explicit

Dim NextTime As Date
Dim ClockRunning As Boolean

Sub StartClock()

    If ClockRunning = True Then Exit Sub
    
    ClockRunning = True
    
    UpdateClock

End Sub


Sub UpdateClock()

    If ClockRunning = False Then Exit Sub

    Range("A1").Value = Time
    Range("A1").NumberFormat = "hh:mm:ss"

    NextTime = Now + TimeValue("00:00:01")
    Application.OnTime NextTime, "UpdateClock"

End Sub


Sub StopClock()

    On Error Resume Next
    
    ClockRunning = False
    
    Application.OnTime NextTime, "UpdateClock", , False

End Sub

Optional: automatically stop when closing Excel

In ThisWorkbook (not Module):

Private Sub Workbook_BeforeClose(Cancel As Boolean)

    StopClock

End Sub

OR...simply as Formula: =NOW()

My answers are voluntary and without guarantee!

Hope this will help you.