Sell up when independence goes, not before (5)
I believe the answer is:
Here is my best explanation:
'before' is the definition.
Both the answer and definition are adverbs. Perhaps they are linked in a way I don't understand?
I can't explain the remainder of the clue.
(Other definitions for later that I've seen before include "Alter (anag.)", "In due course", "behind schedule", "At some further point in time", "At a time in the future", "Alert (anag.)", "Subsequent", "Subsequently", "Afterwards" and "subsequently".)