The day before seven stripped
I believe the answer is:
eve
'the day before' is the definition.
(eve is the night before something)
'seven stripped' is the wordplay.
'stripped' says to take the centre.
The middle letters of 'seven' are 'EVE'.
(Other definitions for eve that I've seen before include "First lady from the night before" , "Period immediately before" , "Mother of Abel" , "Night before an event" , "Day before; first woman" .)