The most common and most likely answer to this crossword clue is the 5 letter word LIPPY
I've seen this crossword clue in Financial Times
L
I
P
P
Y
Buddy explains!
The straight part
We know that "with too much to say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with too much to say = lippy.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does LIPPY mean?
LIPPY adjective- Having prominent lips.
- Having a tendency to talk back in a cheeky or impertinent manner.
- Lip gloss or lipstick; a stick of this product.
- An old dry measure amounting to one quarter of a peck (for goods sold by weight, 1¾ pounds or about four-fifths of a kilogram); also, a container of that capacity.