Blast of wind (4)
'blast of wind' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for gust that I've seen before include "Burst of strong wind" , "A strong current of air" , "Puff (of wind)" , "Blast of air" , "Flurry" .)
(Other definitions for gus that I've seen before include "Augustus (dim.)" , "T. S. Eliot's theatre cat" .)