The most common and most likely answer to this crossword clue is the 7 letter word SUFFICE
I've seen this crossword clue in The Times
S
U
F
F
I
C
E
Buddy explains!

The straight part
We know that "do" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case do = suffice.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 SUFFICE mean?
SUFFICE verb- To be enough or sufficient; to meet the need (of anything); to be adequate; to be good enough.
- To satisfy; to content; to be equal to the wants or demands of.
- To furnish; to supply adequately.