Flower, small at this time prior to fall (8)
I believe the answer is:
snowdrop
'flower' is the definition.
(snowdrop is a kind of flower)
'small at this time prior to fall' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'at this time' becomes 'now' (I've seen this before).
'prior to' means one lot of letters go next to another.
'fall' becomes 'drop' (dropping is a kind of falling).
's'+'now'+'drop'='SNOWDROP'
(Other definitions for snowdrop that I've seen before include "Avalanche perhaps" , "Wood anemone" , "Small white flower of early spring" , "White-flowered plant (Galanthus nivalis)" , "Bulbous plant that flowers in early spring" .)