Equipment developing no rust, etc, came (13)
I believe the answer is:
accoutrements
'equipment' is the definition.
(I've seen this before)
'developing no rust etc came' is the wordplay.
'developing' indicates anagramming the letters.
'no'+'rust'+'etc'+'came'='norustetccame'
'norustetccame' anagrammed gives 'ACCOUTREMENTS'.
(Other definitions for accoutrements that I've seen before include "Trappings" , "clothing" , "Equipment" , "Appurtenances" , "Paraphernalia" .)