### Clue: Wood workers, ones celebrating wildly when rector becomes bishop (9)
### Answer: BEVELLERS 
 ### Explanation: Definition: Wood workers
 "revellers"(ones celebrating wildly) **with** "r"(abbrev. for "rector") **replaced by** "b"(abbrev. for "bishop", say, in chess)( when … becomes …).
Answer: Machines, specifically to cut bevels in timber.