The most common and most likely answer to this crossword clue is the 9 letter word BLACKOUTS
I've seen this crossword clue in Independent
B
L
A
C
K
O
U
T
S
More clues leading to the result BLACKOUTS
Buddy explains!
The straight part
We know that "Periods with deficiency to mind?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case periods with deficiency to mind? = blackouts.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 BLACKOUTS mean?
BLACKOUTS noun- A temporary loss of consciousness.
- A temporary loss of memory.
- An instance of censorship, especially a temporary one.
- A large-scale power failure, and resulting loss of electricity to consumers.
- The mandatory blocking of all light emanating from buildings as imposed during World War II.