Retreat every other time (3)
I believe the answer is:
era
'time' is the definition.
(an era is a period of time)
'retreat every other' is the wordplay.
'every other' means one should take alternating letters (every other letter).
The alternating letters of 'retreat' are 'ERA'.
(Other definitions for era that I've seen before include "Significant time" , "Long historical period" , "Long stretch" , "Cycle" , "Long period of history" .)