Fine lieutenant protecting soldiers in disorder (7)
I believe the answer is:
Here is my best explanation:
'disorder' is the definition.
(ailment is a kind of disorder)
'fine lieutenant protecting soldiers' is the subsidiary indication.
'fine' becomes 'ai' (I've seen this in other clues**).
'lieutenant' becomes 'lt'.
'protecting' indicates putting letters inside.
'soldiers' becomes 'men' (I've seen this before).
'lt' placed around 'men' is 'lment'.
'in' is the link.
(Other definitions for ailment that I've seen before include "Indisposition", "Bodily disorder or disease", "Disorder", "Malady", "Complaint, affliction", "Illness", "Minor illness", "Tim Alen has an odd indisposition.", "Physical disorder" and "Slight but persistent illness".)