The most common and most likely answer to this crossword clue is the 7 letter word BOILING
I've seen this crossword clue in The Sunday Telegraph
B
O
I
L
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More clues leading to the result BOILING
Buddy explains!

The straight part
We know that "Very hot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case very hot = boiling.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 BOILING mean?
BOILING verb- (of liquids) To heat to the point where it begins to turn into a gas.
- To cook in boiling water.
- (of liquids) To begin to turn into a gas, seethe.
- To bring to a boil, to heat so as to cause the contents to boil.
- (used only in progressive tenses, of weather) To be uncomfortably hot.
- (used only in progressive tenses) To feel uncomfortably hot.
- To form, or separate, by boiling or evaporation.
- To steep or soak in warm water.
- To be agitated like boiling water; to bubble; to effervesce.
- To be moved or excited with passion; to be hot or fervid.
- The process of changing the state of a substance from liquid to gas by heating it to its boiling point.
- An animation style with constantly changing wavy outlines, giving a shimmering or wobbling appearance.
- That boils or boil.
- Of a thing: extremely hot or active.
- Of a person: feeling uncomfortably hot.
- Of the weather: very hot.
- (of adjectives associated with heat) Extremely