I don't think there's a Southern line on the London Underground

Nice grid. A few (I hope) constructive points:
There is no Southern line on the London Underground
Beware of repeating clues (Southern here): the system sees them as separate, so someone could get it right but not be rewarded by pure chance (ie chooses the wrong Southern) - it’s a mistake I’ve made myself!
Keep submitting - we all get better over time. I did enjoy this one.

There's no Southern line on the Underground :)

I think it's good to have straightforward easy grids on here for those just starting to do them, and for kids. However, two the Southerns don't work for different reasons and I don't think doormouse is a thing.

*the two*

its 'dormouse'
no southern line
multiple clues don't work!

Enjoyed this one, though do agree with some of the other comments

It's "dOrmouse", not "dOOrmouse"....sorry to be picky:-)

There is no Southern underground line and no such thing as a doormouse.