More stable business with the queen (6)
I believe the answer is:
firmer
'more stable' is the definition.
('firm' can be similar in meaning to 'stable')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for firmer that I've seen before include "not so easy to penetrate?" , "More rigid" , "Stronger" , "Stiffer" , "harder to uproot?" .)