Army unit not finishing course (7)
I believe the answer is:
regimen
'course' is the definition.
(prescribed course of treatment or diet)
'army unit not finishing' is the wordplay.
'army unit' becomes 'regiment' (regiment is a kind of army unit).
'not finishing' means to remove the last letter.
'regiment' with its final letter removed is 'REGIMEN'.
(Other definitions for regimen that I've seen before include "Merge in for prescribed way of life" , "recommended diet" , "Systematic way of life" , "That's what doctor orders" , "Recommended course" .)