The most common and most likely answer to this crossword clue is the 5 letter word ACORN
I've seen this crossword clue in The Times
A
C
O
R
N
More clues leading to the result ACORN
- A scam to snaffle farmer’s last fruit from tree
- A crop that is produced by a tree
- Seed in banana republic to enter Wimbledon, finally
- A grain seed
- Goodness found in an oak seed
- A painful thing for a nut
- Fruit, bacon, unlimited by Royal Navy
- A grain, or fruit
- Seed planted in Armagnac or nearby
- A lot of sailors grasping firm bit of mast
Buddy explains!

The straight part
We know that "bit of mast" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bit of mast = acorn.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 ACORN mean?
ACORN noun- The fruit of the oak, being an oval nut growing in a woody cup or cupule.
- A cone-shaped piece of wood on the point of the spindle above the vane, on the mast-head.
- See acorn-shell.
- (usually in the plural) A testicle.