All drop to bust an arm and a leg (3,6)
I believe the answer is:
top dollar
'arm and a leg' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'all drop to bust' is the wordplay.
'bust' indicates anagramming the letters.
'all'+'drop'+'to'='alldropto'
'alldropto' is an anagram of 'TOP-DOLLAR'.
'an' is the link.
Can you help me to learn more?
(Other definitions for top dollar that I've seen before include "high price?" , "High(est) price" , "The highest sum paid" .)