Slight breaks alarming (8)
I believe the answer is:
marginal
'slight' is the definition.
(thesaurus)
'breaks alarming' is the wordplay.
'breaks' indicates anagramming the letters.
'alarming' with letters rearranged gives 'MARGINAL'.
(Other definitions for marginal that I've seen before include "On the fringes" , "unsafe seat" , "on border" , "On the edges of" , "Peripheral in alarming way" .)