Flaky stuff in follow-on series is sent up (4)
I believe the answer is:
snow
'flaky stuff' is the definition.
(I've seen this in another clue)
'in follow-on series is sent up' is the wordplay.
'in' indicates a hidden word.
'is sent up' is a reversal indicator.
'wons' is hidden within 'follow on series'.
'wons' reversed gives 'SNOW'.
(Other definitions for snow that I've seen before include "Downfall of white" , "that may come at Christmas" , "Wintry precipitation" , "White flakes" , "Crystalised rain" .)