The most common and most likely answer to this crossword clue is the 7 letter word SWEEPER
I've seen this crossword clue in The Times
S
W
E
E
P
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R
More clues leading to the result SWEEPER
Buddy explains!

The straight part
We know that "Cleaner/back" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cleaner/back = sweeper.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 SWEEPER mean?
SWEEPER noun- One who sweeps floors or chimneys.
- A detector (for mines).
- Any of the small, tropical marine perciform fishes of the family Pempheridae, typically with deeply keeled, compressed bodies and large eyes.
- A defender who is the last line of defence before the goalkeeper.
- A person who sweeps the ice ahead of the rock in play.
- A batsman who plays sweep shots.
- A fielding position along the boundary; a fielder in this position.
- A tree that has fallen over a river with branches extending into the water.
- A carpet sweeper.
- (including) A vacuum cleaner.
- (including, Cebu) A group of students tasked at cleaning the homeroom after class dismissal.