Confused East Rye with Rye in the past (10)
I believe the answer is:
yesteryear
'in the past' is the definition.
(I've seen this before)
'confused east rye with rye' is the wordplay.
'confused' indicates anagramming the letters.
'with' is an insertion indicator.
'east'+'rye'='eastrye'
'eastrye' is an anagram of 'yestear'.
'yestear' enclosing 'rye' is 'YESTERYEAR'.
(Other definitions for yesteryear that I've seen before include "Former times" , "The recent past" , "nostalgic time, perhaps" , "Days of old (poet.)" , "Days gone by" .)