Possible Clues:

• Ad lib from retired English politician in shot
• Not prepared to delay, one's out with former partner
• Without preparation, of a speech say
• Not 21 downed in a classical sort of manner (9)
• 19 across leaves the Po here without a practice
• Hungry Exeter MP sadly appears on the spur of the moment
• Offhand former worker briefly given money in Stockholm
• Without planning Post Office is in extreme disarray
• Meet about 10 on the skin and off the cuff
• Old-time engineers unprepared