Diet has military group shedding tons (7)
I believe the answer is:
regimen
'diet' is the definition.
(a diet is a certain eating regimen)
'military group shedding tons' is the wordplay.
'military group' becomes 'regiment' (group of soldiers).
'shedding' indicates named letters should be taken away (shed can mean to lose or cast off).
'tons' becomes 't'.
'regiment' with 't' taken out is 'REGIMEN'.
'has' is the link.
(Other definitions for regimen that I've seen before include "administration" , "Therapeutic programme (of diet and exercise)" , "recommended diet" , "Systematic course of treatment, diet, etc" , "Merge in for prescribed way of life" .)