Watch parts broken easily (5,4)
I believe the answer is:
hands down
'easily' is the definition.
(synonyms)
'watch parts broken' is the wordplay.
'watch parts' becomes 'hands' (second hand, minute hand, hour hand).
'broken' becomes 'down' (both can mean not working).
'hands'+'down'='HANDS-DOWN'
(Other definitions for hands down that I've seen before include "without effort" , "extremely easily" , "producing sentences?" , "with ease" , "Teacher's instruction after question's answered" .)