The most common and most likely answer to this crossword clue is the 5 letter word OINKS
I've seen this crossword clue in Financial Times
O
I
N
K
S
More clues leading to the result OINKS
- Writing material evidently having run out, grunts
- ‘Noise of geese not hard,’ Everyman accepted, producing noise of pigs
- Love writer’s fluid approach to last of Miss Piggy’s comments
- Napoleon’s speech in breaking sanctions
- They emerge from what’s in pens, very big pens
- Dividing common people, new racket from swine?
- Sounds from pens being taken out of two inkstands
- Grunts intermittently to fiend with marksman in the middle
- KO’s resulting in grunts?
- Nothing in Kansas squeals
Buddy explains!

The straight part
We know that "They emerge from what’s in pens" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they emerge from what’s in pens = oinks.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 OINKS mean?
OINKS noun- The sound made by a pig, or an imitation thereof.
- Of a pig or in imitation thereof, to make its characteristic sound.