This weather is too much -- get agitated (5)
I believe the answer is:
sweat
'get agitated' is the definition.
'this weather is too much' is the wordplay.
'is too much' indicates a hidden word (only some letters needed - the rest are 'too much').
'SWEAT' is hidden within 'this weather'.
(Other definitions for sweat that I've seen before include "(Of argument) intense" , "Waste (anag.)" , "Trouble in Australia" , "Salty fluid secreted by glands" , "Perspire" .)