Break a leg in a storm (4)
I believe the answer is:
gale
'storm' is the definition.
(a gale is a windy storm)
'break a leg' is the wordplay.
'break' indicates an anagram.
'a'+'leg'='aleg'
'aleg' anagrammed gives 'GALE'.
'in a' acts as a link.
(Other definitions for gale that I've seen before include "Force 8 wind" , "A wild storm" , "Squall" , "Fierce wind" , "Bille from a bladder" .)