Possible Clues:

• Unlikely to tip
• Hard reading about arithmetic?
• Firm resistance: read all about it
• Stout, last of beer, locked in room
• Solid, like an oak
• Solid work at University perhaps involves Republican
• Strong king in his counting-house?
• Think about head of rival firm
• Read about brewer's last stout?
• Rather thick, putting an R in 'investigate'