### Clue: down Sarcastic communication that was and is painful to get over (6,4)
### Answer: BARBED WIRE 
 ### Explanation: Definition: that was and is painful to get over
 BARBED(sarcastic/deliberately hurtful, descriptive of such a remark) + WIRE(a telegram or cablegram – remember those?).
Double defn: 1st: In those old days, such a hurtful communication was painful to get over/forget; and 2nd: In current times, it is painful to climb/get over this device for preventing encroachment.