Plant needs freezing weather and a bit of rain (8)
I believe the answer is:
snowdrop
'plant' is the definition.
(a snowdrop is a plant)
'freezing weather and a bit of rain' is the wordplay.
'freezing weather' becomes 'snow' (**).
'and' means one lot of letters go next to another.
'a bit of rain' becomes 'drop' (a drop of rain is a bit of rain).
'snow'+'drop'='SNOWDROP'
'needs' is the link.
(Other definitions for snowdrop that I've seen before include "Bulbous plant that flowers in early spring" , "Early bloomer" , "Late winter anemone" , "Early-blooming white flower" , "Avalanche perhaps" .)