The most common and most likely answer to this crossword clue is the 5 letter word PROVE
I've seen this crossword clue in The Guardian
P
R
O
V
E
Buddy explains!

The straight part
We know that "show" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case show = prove.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 PROVE mean?
PROVE verb- To proofread.
- To make resistant, especially to water.
- To allow yeast-containing dough to rise.
- To test the activeness of yeast.
- The process of dough proofing.
- To demonstrate that something is true or viable; to give proof for.
- To turn out; to manifest.
- To turn out to be.
- To put to the test, to make trial of.
- To ascertain or establish the genuineness or validity of; to verify.
- To experience.
- To take a trial impression of; to take a proof of.
- To proofread.
- To make resistant, especially to water.
- To allow yeast-containing dough to rise.
- To test the activeness of yeast.
- To demonstrate that something is true or viable; to give proof for.
- To turn out; to manifest.
- To turn out to be.
- To put to the test, to make trial of.
- To ascertain or establish the genuineness or validity of; to verify.
- To experience.
- To take a trial impression of; to take a proof of.