The most common and most likely answer to this crossword clue is the 8 plus 7 letter word SECURITY BLANKET
I've seen this crossword clue in The Sunday Telegraph
S
E
C
U
R
I
T
Y
B
L
A
N
K
E
T
More clues leading to the result SECURITY BLANKET
- Old city-within-city vacant in Ely? Ultimately thought a source of comfort
- Alien supporting pledge, empty source of comfort
- Protection, comprehensive – a source of comfort
- Source of reassurance provided by MI5 cover?
- Emotional support in reality bunk fabricated within religious cult
- Doctor cures it, still holding empty comforter for child
- Kind of guarantee covering all cases that’s comforting
- Irrationally unstable/rickety thing providing comfort
- Does the VIP feel unsafe without this cover?
- Model cut by English rogue now welcomes impassive one providing reassurance
Buddy explains!
The straight part
We know that "comforter for child" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case comforter for child = security blanket.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.