Possible Clues:

• It's a nuisance with the French to make ground in 9 across
• What a nuisance with the French to work with the mortar
• What a nuisance the French can be with the mortar
• Mashing instrument
• Small club for pounding substance in mortar
• Grinder - insect perhaps getting leaf half destroyed
• Small club for use with mortar
• Kitchen implement to be had for a pound
• Pulveriser of nasty insect left on back of house
• What a nuisance to get the French to work with 9 across!