Military body shedding tons in diet (7)
I believe the answer is:
regimen
'diet' is the definition.
(a diet is a certain eating regimen)
'military body shedding tons' is the wordplay.
I cannot really understand how this works, but
'military' could be 're' (I've seen this in other clues) and 're' is found within the answer.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for regimen that I've seen before include "Government - course of treatment" , "Recommended course" , "Merge in (anag.)" , "That's what doctor orders" , "Systematic way of life" .)