Government trimmed part of the army (7)
I believe the answer is:
regimen
'government' is the definition.
(I've seen this before)
'trimmed part of the army' is the wordplay.
I cannot really understand how this works, but
'part' could be 're' (re is a kind of part) and 're' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for regimen that I've seen before include "That's what doctor orders" , "System of diet etc" , "Method of working" , "discipline" , "Prescribed way of life like diet" .)