Flurry of snow in top observation post (5,4)
I believe the answer is:
crows nest
'observation post' is the definition.
(observation post on a ship)
'flurry of snow in top' is the wordplay.
'flurry of' is an anagram indicator (I've seen 'flurried' mean this).
'in' indicates putting letters inside.
'top' becomes 'crest' (crest can mean the top of a hill).
'snow' is an anagram of 'owsn'.
'owsn' going within 'crest' is 'CROWS-NEST'.
(Other definitions for crows nest that I've seen before include "lookout post" , "elevated lookout platform" , "high naval post" .)