Drinks consumed by old king leading to breakdown (8)
I believe the answer is:
collapse
'breakdown' is the definition.
('collapse' can be a synonym of 'breakdown')
'drinks consumed by old king' is the wordplay.
'drinks' becomes 'laps' (lapping is a kind of drinking).
'consumed by' is an insertion indicator.
'old king' becomes 'cole'.
'laps' placed within 'cole' is 'COLLAPSE'.
'leading to' acts as a link.
(Other definitions for collapse that I've seen before include "Fall down unconscious" , "fold" , "Fall down as from weakness" , "Fall down suddenly like escallop" , "Give way, fail suddenly" .)