The most common and most likely answer to this crossword clue is the 3 plus 7 letter word FOR EXAMPLE
I've seen this crossword clue in The Daily Telegraph
F
O
R
E
X
A
M
P
L
E
More clues leading to the result FOR EXAMPLE
- On having cracked puzzle, enough to demonstrate my point
- First ten enough, say
- Say money changing's substantial
- About to crack puzzle that’s big, say
- Say word of warning to players, having got cross enough
- Say more than enough on foreign exchange
- Say at length in English what’s hidden in the grid
- Backing of king sufficient, say
- Like warning Liberal about vote
- On account of test, short prayer required, say
Buddy explains!
The straight part
We know that "say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case say = for example.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.