Alternate alternately, before Easter (4)
I believe the answer is:
lent
'before easter' is the definition.
(I've seen this in another clue)
'alternate alternately' is the wordplay.
'alternately' indicates alternate letters.
The alternate letters of 'alternate' are 'LENT'.
(Other definitions for lent that I've seen before include "Gave the use of for a time" , "Period of fasting" , "Gave for a limited period" , "Period of penance" , "Pre-Easter period" .)