answers all connected with hundreds and thousands:
1. number - not kitten - is c (7)
2. sounds like an opera cable, c above sea level (6.4)
3. dial that sent off the M fleet (5)
4. we'll march to carlisle (3.7.6)
5. PS3 crone companion (3.7.6)
6. Archipelago in canada putting clothes on (8.6.8)
and
7. MI sirs, we hear (3.8.3.3.6)