Works out and breaks down (6)
I believe the answer is:
cracks
I believe this is a double definition.
'works out' is the first definition.
'breaks down' is the second definition.
'and' acts as a link.
(Other definitions for cracks that I've seen before include "Splits; quips" , "'Fractures, splits (6)'" , "They're how the light gets in, according to Leonard Cohen" , "Attempts" .)