Clue: Given up — I'm one to leave military body with honour in retirement (9)
Answer: IMMOLATED
Explanation: Definition: Given up
definition: 'given up' as in 'offered up' as a sacrifice 
I'M, plus reversal/"in retirement" of DETA-i-L plus OM (Order of Merit, "honour")
 
'detail'="military body", minus I="one"