The most common and most likely answer to this crossword clue is the 4 plus 2 letter word JUST SO
I've seen this crossword clue in Independent
J
U
S
T
S
O
More clues leading to the result JUST SO
- Takes part in tournament, with lowest score placed last? Exactly
- Neat, I agree
- Enters the lists with nothing out of place? Exactly
- Fair, therefore bang on
- I agree nothing should be dropped from medieval shows
- Unbiased, very much like some stories for children
- Gravy tastes simply outstanding for starters – that’s as it should be
- In a precise manner, tilts to move ring to the bottom
- Only two elements, to be precise
- Precisely, I agree!
Buddy explains!

The straight part
We know that "I agree" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i agree = just so.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.