The most common and most likely answer to this crossword clue is the 7 letter word OUTAGES
I've seen this crossword clue in The Times
O
U
T
A
G
E
S
More clues leading to the result OUTAGES
Buddy explains!
The straight part
We know that "when torches may be necessary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case when torches may be necessary = outages.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 OUTAGES mean?
OUTAGES noun- A temporary suspension of operation, especially of electrical power supply.
- The amount of something lost in storage or transportation.