Alter assembly at a more advanced stage (5)
I believe the answer is:
later
'at a more advanced stage' is the definition.
I can't judge whether this definition defines the answer.
'alter assembly' is the wordplay.
'assembly' is an anagram indicator.
'alter' is an anagram of 'LATER'.
Can you help me to learn more?
(Other definitions for later that I've seen before include "after an interval" , "At a subsequent time" , "At a time in the future" , "Eventually" , "Following" .)