Work, operate (8)
I believe the answer is:
function
I believe this is a double definition.
'work' is the first definition.
(synonyms)
'operate' is the second definition.
(synonyms)
(Other definitions for function that I've seen before include "Operate" , "Special purpose or social affair" , "An official ceremony" , "What a thing is used for" , "Special task - role" .)