Go downhill: avoid losing pressure (3)
I believe the answer is:
ski
'go downhill' is the definition.
(I've seen this before)
'avoid losing pressure' is the wordplay.
'avoid' becomes 'skip' (I've seen this before).
'losing' is a deletion indicator.
'pressure' becomes 'p' (abbreviation).
'skip' with 'p' removed is 'SKI'.
(Other definitions for ski that I've seen before include "Alpine runner" , "Narrow runner for snow and water" , "Winter sport equipment" , "Winter sports footwear" , "Winter sports item" .)