The most common and most likely answer to this crossword clue is the 5 letter word MATEY
M
A
T
E
Y
Buddy explains!
The straight part
We know that "chum" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chum = matey.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 MATEY mean?
MATEY noun- The conclusive victory in a game of chess that occurs when an opponent's king is threatened with unavoidable capture.
- (by extension) Any losing situation with no escape; utter defeat.
- A fellow, comrade, colleague, partner or someone with whom something is shared, e.g. shipmate, classmate.
- (especially of a non-human animal) A breeding partner.
- A friend, usually of the same sex.
- Friendly term of address to a stranger, usually male, of similar age
- In naval ranks, a non-commissioned officer or his subordinate (e.g. Boatswain's Mate, Gunner's Mate, Sailmaker's Mate, etc).
- A ship's officer, subordinate to the master on a commercial ship.
- A first mate.
- A technical assistant in certain trades (e.g. gasfitter's mate, plumber's mate); sometimes an apprentice.
- The other member of a matched pair of objects.
- A suitable companion; a match; an equal.
- The abovementioned plant; the leaves and shoots used for the tea
- A fellow sailor; often used affectedly, especially as a pirate.
- Sociable or friendly.
- An evergreen tree, Ilex paraquariensis, native to South America, cultivated for its leaves.
- A beverage, resembling tea, made from the dried leaves of this plant.
- A cup of this drink.