Serious blows as leg broken (5)
I believe the answer is:
gales
'serious blows' is the definition.
(I've seen this in another clue)
'as leg broken' is the wordplay.
'broken' indicates an anagram.
'as'+'leg'='asleg'
'asleg' anagrammed gives 'GALES'.
(Other definitions for gales that I've seen before include "Force 7 to 10 winds" , "They're force 7 to 10 on the Beaufort scale" , "High winds" , "Tempests and squalls" , "Weather conditions" .)