1,000-ampere rain protection (4)
I believe the answer is:
gamp
'rain protection' is the definition.
(umbrella)
'1000-ampere' is the wordplay.
'1000' becomes 'G' (G can mean a grand - 1000 pounds, dollars etc).
'ampere' becomes 'amp' (synonyms).
'g'+'amp'='GAMP'
(Other definitions for gamp that I've seen before include "Waterproof cover" , "Umbrella (inf)" , "Midwife" , "Umbrella (from Dickens character)" .)