Only Connect clues

[Barnard]

Trunk, Sap, Surgeon and Top can be preceded by TREE.

[Bertie]

Well spotted, Barnard. Though I went with House as the fourth, with Sap a red herring.

Which just leaves the changing / adding / removing a letter group: Spit, Sap, Mash, Hatter.

[Barnard]

I never thought of tree house which is a far better answer than tree sap.

[Courtenay]

Add a letter to make Split, Snap, Smash and Shatter, which are all words for breaking something?

[Bertie]

Yes, that's it. Well done, Courtenay.

[Courtenay]

I wouldn't have got it without the hint!

[Bertie]

I'm running out of the walls I thought up a little while ago, and onto the ones I'm less happy with. I'll try to think up some more soon, but for now...

Keepsake. Congo. New. Bank.
Terrier. Soviets. Begin. Nottingham.
Rain. Newport. Tibet. Vikings.
America. Tea. Forum. Black.

[Courtenay]

KeepSAKE, BeGIN, NewPORT and FoRUM all end with an alcoholic drink.

[Bertie]

Well spotted.

Congo. New. Bank.
Terrier. Soviets. Nottingham.
Rain. Tibet. Vikings.
America. Tea. Black.

[Barnard]

Four forests.
New, Nottingham, Rain and Black.

[Bertie]

Yep. Spot on.

Remaining clues:

Congo. Bank.
Terrier. Soviets.
Tibet. Vikings.
America. Tea.

[Bertie]

These are quite tricky so I'll give some hints. I did worry about one of the connections, especially - though I've seen a few references to it on my time here so I hoped it might be gettable.

The one I refer to has a literary link. The clues appear in the titles. The other is a word one, putting the same thing before or after each clue.

[Barnard]

Without checking I think there may be be some Tintin book titles.
Land of the Soviets was one and I think Tintin in Tibet.
The others are probably Congo and America.
That may be correct.

[Bertie]

Yes, that's it, Barnard. Well remembered.

Which just leaves putting a word before or after each of: Bank.
Terrier. Vikings. Tea.

[Barnard]

Yorkshire can precede Tea, Bank and Terrier.
I assume it can also precede Vikings.