The most common and most likely answer to this crossword clue is the 9 letter word FLASHCARD
I've seen this crossword clue in Independent
F
L
A
S
H
C
A
R
D
Buddy explains!
The straight part
We know that "learning aid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case learning aid = flashcard.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 FLASHCARD mean?
FLASHCARD noun- A card used to aid rote memorization. One side of the card contains data of one kind, or a question, and the other side contains the associated response which one wants to memorize. For example, one side could contain an English word, and the other side the Spanish translation.
- A solid state digital memory storage format, commonly found on computers, digital cameras and cellphones.