Henry's cryptic

123456
Across
  1. 3. First Canadian youths (Alex + Joe) could have been... robot?
  2. 5. dissent ended batters inning but first she hit.
  3. 6. Hydrogen tipped shooting equipment found in fancy British school.
Down
  1. 1. first of big elephants could add up sums easily due to?
  2. 2. attempt to score in rugby.
  3. 4. fat guy left in vehicle?
  4. 5. child up chimney hit cricket shot.