Temper made Gauss add brackets the wrong way (7)
I believe the answer is:
assuage
'temper' is the definition.
(I've seen this in another clue)
'made gauss add brackets the wrong way' is the wordplay.
'brackets' indicates the answer is hidden within the clue (the answer is contained or bracketed by the clue).
'the wrong way' says the letters should be written in reverse.
'egaussa' can be found hidden inside 'made gauss add'.
'egaussa' reversed gives 'ASSUAGE'.
(Other definitions for assuage that I've seen before include "Sausage (anag.)" , "'Alleviate, appease (7)'" , "Provide physical or mental relief -- satisfy" , "Satisfy (a desire)" , "Reduce severity" .)