Confused a year with a smaller period (3)
I believe the answer is:
day
'a smaller period' is the definition.
'day' can be an answer for 'period' (day is a kind of period). I am unsure of the 'a smaller' bit.
'confused a year with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'DAY' is hidden in the letters of 'confused a year'.
Can you help me to learn more?
(Other definitions for day that I've seen before include "Period of time" , "24 hour period" , "Lewis as poet" , "Dawn to dusk" , "Twenty-four hours" .)