Possible Clues:

• Tenuous
• The omnibus has overturned, so let it be broken in no obvious way
• Let off after bus reversed - it's so understated you wouldn't even notice it!
• None too obvious
• Barely perceptible
• Able to make fine distinctions
• Delicately understated
• The bus overturns. Let it be broken in no simple way
• Bustle about, being slight and difficult to analyse
• Not so simple to have sublet this