The most common and most likely answer to this crossword clue is the 7 letter word INSTILL
I've seen this crossword clue in The Daily Telegraph
I
N
S
T
I
L
L
More clues leading to the result INSTILL
Buddy explains!

The straight part
We know that "to teach" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to teach = instill.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 INSTILL mean?
INSTILL verb- To cause a quality to become part of someone's nature.
- To pour in (medicine, for example) drop by drop.