The most common and most likely answer to this crossword clue is the 5 letter word CHALK
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Buddy explains!
The straight part
We know that "I’m given much to do on board" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i’m given much to do on board = chalk.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 CHALK mean?
CHALK noun- A soft, white, powdery limestone.
- A piece of chalk, or nowadays processed compressed gypsum, that is used for drawing and for writing on a blackboard.
- Tailor's chalk.
- A white powdery substance used to prevent hands slipping from holds when climbing, sometimes but not always limestone-chalk.
- A platoon-sized group of airborne soldiers.
- (horseracing) The favorite in a sporting event.
- The prediction that there will be no upsets, and the favored competitor will win.
- To apply chalk to anything, such as the tip of a billiard cue.
- To record something, as on a blackboard, using chalk.
- To use powdered chalk to mark the lines on a playing field.
- To record a score or event, as if on a chalkboard.
- To manure (land) with chalk.
- To make white, as if with chalk; to make pale; to bleach.