Naval officers having standards (7)
I believe the answer is:
This clue is a double definition.
'naval officers' is the first definition.
(I've seen this before)
'standards' is the second definition.
'having' is the link.
(Other definitions for ensigns that I've seen before include "US naval officers", "Old soldiers", "(Military) flags", "officers? Of lower rank", "Flags for naval officers".)