Subsequently alter shape (5)
I believe the answer is:
later
'subsequently' is the definition.
(subsequently means later on)
'alter shape' is the wordplay.
'shape' is an anagram indicator.
'alter' with letters rearranged gives 'LATER'.
(Other definitions for later that I've seen before include "At a subsequent time" , "Tomorrow (or next week)?" , "succeeding" , "Following" , "In due course" .)