Possible Clues:

• Doubting
• Inclined not to believe
• Start to saute mushroom with a light touch: it sounds dubious
• Cecil's apt to become suspicious
• Doubtful
• Unwilling to give credit
• This type finds it hard to swallow anything not solid
• Inclined to disbelieve, not convinced
• Not at all keen to give credit
• Foolishly accepts about one pound that's dubious