London Underground Stations

[potterer]

Would welcome help with the following please.
1. Marks the pudding.
2. Built too small for the palace.
3. Hunker down on this incline.
4. Yellow warbler sings here.

[emeritus]

1 Monument

[emeritus]

4 Canary Wharfe

[emeritus]

sorry Wharf

[madmick]

4. Canary Wharf

[emeritus]

3 Crouch Hill

[elliemay1]

3 Crouch Hill?

[New Judge]

I cannot get cryptic crossword clues (they always seem obscure and sometimes ridiculous to me). However, I do know a lot about the London Underground and there is no station at Crouch Hill. There is a station of that name on the London Overground system between Upper Holloway and Harringay (Green Lanes) on the Gospel Oak to Barking line.

[Hopkirk]

The overground line does appear on the Underground map though, NJ

[potterer]

Thanks for your help. I agree Crouch hill fits the clue even though the answers are meant to be underground.
Just leaves no 2 now.

[grasscarp]

2 Marble Arch
originally constructed for Buckingham Palace. One story was that the Royal Coach could not pass through as it was too narrow.