Clue: Lord's guard hit hard with chair support (6-3-3)
Answer: MIDDLE-AND-LEG
Explanation: Definition: Lord's guard

**MIDDLE** (hit hard, in cricket, i.e. strike the ball with the middle of the bat) + **AND** ("with") + **LEG** ("chair support")
 

 
*Lord's is a famous London cricket ground, so the solution is related to cricket. Middle-and-leg is a stance taken by a batsman as he awaits the ball to be bowled, in which his bat is initially guarding the middle and leg stumps.