Member of Weight Watchers, German chap? (6)
I believe the answer is:
dieter
I believe this is a double definition.
'member of weight watchers' is the first definition.
(someone one a diet)
'german chap?' is the second definition.
(common German name)
(Other definitions for dieter that I've seen before include "German male" , "who's getting slimmer?" , "One who's slimming" , "fellow who'll eat less?" , "The weight-watcher" .)