Equipment developing no rust, etc, came (13)
I believe the answer is:
Here is my best explanation:
'equipment' is the definition.
(I've seen this before)
'developing no rust etc came' is the subsidiary indication.
'developing' indicates anagramming the letters.
'norustetccame' with letters rearranged gives 'accoutrements'.
(Other definitions for accoutrements that I've seen before include "Paraphernalia", "Equipment", "Trappings", "Soldiers outfit other than weapons and garments", "Appurtenances" and "Gear".)