Erode it at one burst (3,4)
I believe the answer is:
eat into
'erode' is the definition.
(I've seen this in another clue)
'it at one burst' is the wordplay.
'burst' indicates an anagram.
'it'+'at'+'one'='itatone'
'itatone' anagrammed gives 'EAT INTO'.
(Other definitions for eat into that I've seen before include "run down" , "Etch" , "Consume (resources)" , "start wearing out" , "Corrode (something)" .)