The most common and most likely answer to this crossword clue is the 8 letter word MEDITATE
I've seen this crossword clue in The Guardian
M
E
D
I
T
A
T
E
More clues leading to the result MEDITATE
- Contemplate friend consuming awful diet
- Reflect upon friend taking rewrite on board
- Deliberate tackle initially accepted by referee
- Think to behave diplomatically? About time!
- Think deeply about time-consuming referee
- Reflect, seeing change in friend
- Reflect and act as go-between? About time
- Referee took time to ponder
- Referee taking time to think
- Think to behave dipomatically? About time!
Buddy explains!

The straight part
We know that "think" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case think = meditate.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 MEDITATE mean?
MEDITATE verb- To contemplate; to keep the mind fixed upon something; to study.
- To sit or lie down and come to a deep rest while still remaining conscious.
- To consider; to reflect on.