Extra work (3,4)
(Other definitions for bit part that I've seen before include "'Small role in film or play (3,4)'" , "Small acting role" , "cameo" , "Tool" , "extra work, perhaps" .)
I believe this is a double definition.
'extra' is the first definition.
(extra is a type of cricket run)
'work?' is the second definition.
(both can mean to operate something)
(Other definitions for run that I've seen before include "Possibly an extra" , "Move at speed" , "publish" , "Manage, operate" , "On the . . . - fleeing from pursuit" .)