Answer:

reducer

Answer	Crossword Clue
REDUCER	Oxidizing solution, in photography
REDUCER	One on a diet
REDUCER	Pipe fitting

REDUCER	Photo-lab liquid
REDUCER	Curtailer.
REDUCER	Calorie counter.
REDUCER	Eschewer of starches.
REDUCER	Calorie watcher.
REDUCER	Dieter.
REDUCER	Weight-watching person
REDUCER	Dieter

REDUCER	One losing weight