Possible Clues:

• Six in Ireland capture one, for example for the blockade
• Besetting sin, not trendy, say, within limits of indolence
• Preattack tactic
• Prolonged attack on a fortified place
• That'll cause trouble enough to spoil 27 across
• You're being attacked while under it
• "Dog Day Afternoon" event
• Long series of troubles
• Gee! Is this a complicated takeover campaign?
• Blockade of a fortified place