The most common and most likely answer to this crossword clue is the 8 letter word GOLDFISH
I've seen this crossword clue in The Times
G
O
L
D
F
I
S
H
More clues leading to the result GOLDFISH
- Little swimmer’s winning medal, initially for his swimming
- Head for Google: previous search one supposedly forgot quickly
- Au fait to occasionally ignore quiet pet, perhaps
- Bond villain’s not half one to take tips from Smersh — he may go round in a tank
- Game is hard, daughter admitted — swimmer with severe limitations?
- Fair prize perhaps for a little swimmer
- Beginning to drive in VW is hard for one in tank?
- Swimmer ultimately recognising mature following is hot!
- Old 10 embracing the same foxtrot — is one’s memory short?
Buddy explains!

The straight part
We know that "Little swimmer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case little swimmer = goldfish.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 GOLDFISH mean?
GOLDFISH noun- A type of small fish, Carassius auratus, typically orange-colored.