Possible Clues:

• Admission of defeat left a revolutionary in grip of former Liberal
• Symbol of surrender
• For those looking to talk about War of Attrition, it needs to be raised before start at Leopardstown
• A few light struggles? This shows I surrender
• Waved banner hinted at by the ends of 17-, 36- and 42-Across
• Chess player, following delay, giving in token
• Light a few flares as signal to enemy?
• Standard of negotiation
• First five characters in 6 down from The Banner provided admission of defeat
• Sign of giving up after a few light exercises