Ignoring individual, sell up afterwards (5)
I believe the answer is:
later
'afterwards' is the definition.
(I know that afterwards can be written as later)
'ignoring individual sell up' is the wordplay.
'ignoring' suggests deleting specific letters.
'individual' becomes 'i' (Roman numeral for one).
'sell' becomes 'retail' (retailing is a kind of selling).
'up' is a reversal indicator (in down clue: letters go upwards).
'retail' with 'i' removed is 'retal'.
'retal' back-to-front is 'LATER'.
(Other definitions for later that I've seen before include "After a given point in time" , "At a subsequent time" , "after the rest?" , "more modern" , "behind schedule" .)