Possible Clues:

• Firm's board coming to conclusion of business
• Firm providing accommodation for Arabs, perhaps
• Racehorses certainly not foaming at the mouth?
• Resisting chemical change
• Firmly fixed equine lodgings
• The real centre of the household, said GBS
• A number of people represented by the same company or firm
• Bleats could come from this
• Sty : hogs :: ___ : horses
• Under control