The most common and most likely answer to this crossword clue is the 7 letter word HEARTHS
I've seen this crossword clue in The Sunday Telegraph
H
E
A
R
T
H
S
Buddy explains!

The straight part
We know that "warm indoor locations" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case warm indoor locations = hearths.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 HEARTHS mean?
HEARTHS noun- A brick, stone or cement floor to a fireplace or oven.
- An open recess in a wall at the base of a chimney where a fire may be built.
- The lowest part of a metallurgical furnace.
- A brazier, chafing dish, or firebox.
- Home or family life.
- A household or group in some forms of the modern pagan faith Heathenry.