The most common and most likely answer to this crossword clue is the 6 letter word NAPALM
I've seen this crossword clue in Financial Times
N
A
P
A
L
M
More clues leading to the result NAPALM
- Weapon, and where it was used around China
- Man up to swallow friend's fiery concoction
- Weapon round backed for use in Vietnam
- It spells end of vegetation, when put on a tree
- Name a magician’s move something incendiary
- Sodium on tree is cause of fire in vegetation
- Incendiary substance China used in war
- Chemical weapon produced by friend entering conflict involving US
- Almost snatch and grab sticky jelly
- Ally in war zone shows weapon there
Buddy explains!

The straight part
We know that "sticky jelly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sticky jelly = napalm.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 NAPALM mean?
NAPALM noun- A highly flammable, viscous substance, designed to stick to the body while burning, used in warfare as an incendiary especially in wooded areas.
- To spray or attack with this substance.