White pile ground down first (9)
I believe the answer is:
snowdrift
'white pile' is the definition.
'snowdrift' can be an answer for 'pile' (thesaurus). I'm unsure of the 'white' bit.
'ground down first' is the wordplay.
'ground' indicates anagramming the letters ('grind' the letters into a new form).
'down'+'first'='downfirst'
'downfirst' is an anagram of 'SNOWDRIFT'.
Can you help me to learn more?
(Other definitions for snowdrift that I've seen before include "Midwinter may show one" , "Winter problem" , "Feature of winter weather" , "Wintry feature" , "evidence of wintry weather" .)