The most common and most likely answer to this crossword clue is the 6 letter word BAKING
I've seen this crossword clue in The Daily Telegraph
B
A
K
I
N
G
More clues leading to the result BAKING
- Still of cook filling container with blood
- Degree to which 27 may become very hot
- Really warm support Conservative lost
- Extremely hot theme in Hollywood TV shows
- Very hot support Conservative’s lost
- Appropriate to take stock of a cooking method
- Biscuits and bread made by this royal academician!
- Chef’s ability with receptacle inspiring people
- Cooking a bannock finally in Crosby
- Cup of tea inspiring family activity in kitchen
Buddy explains!

The straight part
We know that "Really warm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case really warm = baking.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 BAKING mean?
BAKING verb- (with person as subject) To cook (something) in an oven.
- (with baked thing as subject) To be cooked in an oven.
- To be warmed to drying and hardening.
- To dry by heat.
- To be hot.
- To cause to be hot.
- To smoke marijuana.
- To harden by cold.
- To fix (lighting, reflections, etc.) as part of the texture of an object to improve rendering performance.
- (with "in" or "into") To incorporate into something greater.
- An action in which something is baked.
- The way in which something is baked.
- The production of a batch of baked product.
- That bakes.
- Of a person, an object, or the weather: very hot; boiling, broiling, roasting.