The most common and most likely answer to this crossword clue is the 5 letter word FREES
I've seen this crossword clue in The Guardian
F
R
E
E
S
Buddy explains!

The straight part
We know that "Lets out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lets out = frees.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 FREES mean?
FREES noun- Free transfer
- The usual means of restarting play after a foul is committed, where the non-offending team restarts from where the foul was committed.
- To make free; set at liberty; release.
- To rid of something that confines or oppresses.
- (other ballgames) a kick in which a player may kick the ball without interference from the opposition. Such a kick may be awarded for a foul by the opposition, or earned by a player such as by taking a mark.
- The usual means of restarting play after a foul is committed, where the non-offending team restarts from where the foul was committed.