Winter pileup (9)
I believe the answer is:
snowdrift
'winter pileup' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for snowdrift that I've seen before include "Midwinter may show one" , "Winter problem" , "Wind-driven winter hazard" , "Weather problems" , "Wintry feature" .)