Possible Clues:

• See 41-Across
• See 13
• See 20-Across
• A blow below . . . . . . . is a foul in boxing
• In boxing, a punch below ... .... is a foul
• In boxing, it's a foul to punch below ... ....
• Don't hit below ... ....; it's a foul
• Don't hit below . . . . . - it's a foul