The '90s, for one (6)
I believe the answer is:
decade
'the '90s for one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for decade that I've seen before include "The noughties, say" , "Group of ten things" , "The 1960s, for example" , "number of years" , "Ten-year period" .)