Sub crossword

123456
Across
  1. 2. to take away numbers in maths
  2. 5. under water
  3. 6. a material
Down
  1. 1. a place were you sign up for something
  2. 3. a place underground with trains
  3. 4. someone is the boss of you
  4. 5. a heading you put below your heading in writing