Herald 2

[dave1948]

18a High collar protects not at all in a flow of excess water (6)
R?N?F?

23a Four extreme characters chew the fat ? (4)
C?A?

[bookbinder]

18 runoff

[sandyRoe]

23 chat

[bookbinder]

23 I think that it might be chaw.
http://www.thefreedictionary.com/chaw

[dave1948]

Thank you

Any explanation of chaw or chat ?

[bookbinder]

Four extreme characters = cha(at beginning of characters) + w (at opposite end of chew). If you actually chew/chaw a lump of fat, you probably don't intend to swallow it, which fits with my link. QED

[sandyRoe]

CH ew f AT

[bookbinder]

It looks like dictionaries at dawn, sandy.

[sandyRoe]

We need somebody who takes the Herald to come back tomorrow and settle this. :-)