The most common and most likely answer to this crossword clue is the 3 letter word ANA
I've seen this crossword clue in The Times
A
N
A
Buddy explains!

The straight part
We know that "collection of reminiscences" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case collection of reminiscences = ana.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 ANA mean?
ANA noun- A collection of things associated with a person or place, especially a personal collection of anecdotes or conversations at table
- (in prescriptions) Of each; an equal quantity.
- Anorexia (used especially by the pro-ana movement).
- In a direction analogous to up, but along the additional axis added by the fourth dimension.
- A unit of currency in former British India equal to 12 pies or 1/16 rupee.