The most common and most likely answer to this crossword clue is the 5 letter word SWABS
I've seen this crossword clue in The Daily Telegraph
S
W
A
B
S
Buddy explains!
The straight part
We know that "Mops" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mops = swabs.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 SWABS mean?
SWABS noun- A small piece of soft, absorbent material, such as gauze, used to clean wounds, apply medicine, or take samples of body fluids. Often attached to a stick or wire to aid access.
- A sample taken with a swab (piece of absorbent material).
- A piece of material used for cleaning or sampling other items like musical instruments or guns.
- A mop, especially on a ship.
- A sailor; a swabby.
- A naval officer's epaulet.
- To use a swab on something, or clean something with a swab.