Clue: What helps bowlers hit their mark? (4)
Answer: BIAS
Explanation: Definition: What helps bowlers hit their mark
A bit of a stab in the dark: I think this refers to the bias in the balls in the game of bowls, which either helps or hinders hitting the jack, depending on the player's skill level. Not very helpful to have a rather vague crptic defnitiion whose last letter is crucial to the ambiguous 10a