Fate is fulfilled after end of luck (6)
I believe the answer is:
kismet
'fate' is the definition.
(kismet is a kind of fate)
'is fulfilled after end of luck' is the wordplay.
'fulfilled' becomes 'met' ('meet' can be a synonym of 'fulfil').
'after' says to put letters next to each other.
'end of' says to take the final letters.
The final letter of 'luck' is 'k'.
'is'+'met'='ismet'
'ismet' after 'k' is 'KISMET'.
(Other definitions for kismet that I've seen before include "Turkish fate, destiny" , "fortune" , "Broadway musical" , "lot in life" , "Destiny; 50s musical" .)