Celebrate rising machine operator (5)
I believe the answer is:
lever
'machine operator' is the definition.
(I've seen this before)
'celebrate rising' is the wordplay.
'celebrate' becomes 'revel' (reveling is a kind of celebrating).
'rising' shows that the letters should be reversed in order (going up in a down clue).
'revel' backwards is 'LEVER'.
(Other definitions for lever that I've seen before include "Crowbar" , "Kind of bar for prising or lifting" , "Prize" , "Rod" , "Rigid bar pivoting about a fulcrum" .)