Work up to the end of April (4)
I believe the answer is:
till
'work' is the definition.
(to till is to work the land)
'up to the end of april' is the wordplay.
'up to' becomes 'til' (I've seen this in another clue).
'the end of' indicates one should take the final letters.
The final letter of 'april' is 'l'.
'til'+'l'='TILL'
(Other definitions for till that I've seen before include "To the time of the money drawer" , "cash container" , "Money box" , "Small box in shop for holding cash" , "Up to (a point in time)" .)