Crossword puzzle clue "stage action reaction perhaps"

Stage-action reaction, perhaps

It doesn't convey ferocious fuel-burning action, action, action! when it's regular-sized

Reciprocal action and reaction

Action that may produce a reaction

Piece of the action, or a shout that stops the action

Who said "Action may not always bring happiness, but there is no happiness without action."

Elaborate Broadway stage decor, vis-a-vis summer camp theater stage design?

At an early stage — at a late stage