The most common and most likely answer to this crossword clue is the 6 letter word ISOPOD
I've seen this crossword clue in The Guardian
I
S
O
P
O
D
More clues leading to the result ISOPOD
- Woodlouse, perhaps, one by flower in turf
- Eg woodlouse I originally saw on seedcase
- I work in turfy ground, finding woodlouse, for example
- Is old shell a crustacean?
- One unpleasant person outside work, one with fourteen members
- Shuffle, say, round well to find creeper
- Poseidon banishing east and north winds to find 1
- Bug I steep in alcohol on demand
- Lousy type in party place, half cut, rolling over
- Is operation connected with overdose – it may give the creepy-crawlies?
Buddy explains!

The straight part
We know that "one with fourteen members" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one with fourteen members = isopod.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 ISOPOD mean?
ISOPOD noun- Any of very many crustaceans, of the order Isopoda, that have a flattened body and no carapace.