The most common and most likely answer to this crossword clue is the 5 letter word CAPON
I've seen this crossword clue in The Guardian
C
A
P
O
N
More clues leading to the result CAPON
- Restriction applying to poultry
- Chicken in vessel crossing river
- Fattened fowl a gang leader left unfinished
- Chicken backing away from gangster
- A fattened victim of castration, so headwear in place
- Vessel crossing river brings chicken
- Chicken wearing hat?
- Cockerel made man nervous at first
- Fowl with head covered?
- Protection against kids worn by a big chicken
Buddy explains!

The straight part
We know that "Fowl" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fowl = capon.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 CAPON mean?
CAPON noun- A cockerel which has been gelded and fattened for the table.
- To castrate; to make a capon of.