The most common and most likely answer to this crossword clue is the 9 letter word FOSTERAGE
I've seen this crossword clue in The Daily Telegraph
F
O
S
T
E
R
A
G
E
Buddy explains!

The straight part
We know that "Nurture" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nurture = fosterage.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 FOSTERAGE mean?
FOSTERAGE noun- The act of fostering another's child as if it were one's own.
- The act of caring for another human being or animal.
- The condition of being the foster child.
- The act of promoting or encouraging something.