Spray son parking in heap of snow (9)
I believe the answer is:
spindrift
'spray' is the definition.
(I know that spindrift is a type of spray)
'son parking in heap of snow' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'parking' becomes 'p' (abbreviation on road signs).
'heap of snow' becomes 'drift' (snowdrift).
's'+'p'+'in'+'drift'='SPINDRIFT'
(Other definitions for spindrift that I've seen before include "Fine snow driven by the wind" , "A bit wet, but deep underneath" , "Spray blown along surface of sea" , "current into spray" .)