The most common and most likely answer to this crossword clue is the 4 plus 5 letter word HOLD FORTH
I've seen this crossword clue in Financial Times
H
O
L
D
F
O
R
T
H
More clues leading to the result HOLD FORTH
- Stay on river, so to speak
- Take centre stage in talk show
- Show where ship’s cargo’s put on river
- Go on about the job of the banks in Alloa?
- Successfully defend river and speak at length
- Speak at length from keep on Scottish river
- Talk on “Harbours harbouring old stronghold”
- Argue to take ancient stronghold within hours
- Talk at length to reserve the tower with the husband
- Couple of husbands touring prehistoric castle speak at length
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 = hold forth.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.