Wasting time, I exported nasty bleach (8)
I believe the answer is:
peroxide
'bleach' is the definition.
(type of bleach)
'wasting time i exported nasty' is the wordplay.
'wasting' indicates named letters should be taken away.
'time' becomes 't' (abbreviation).
'nasty' indicates anagramming the letters.
'i'+'exported'='iexported'
'iexported' with 't' taken away is 'iexpored'.
'iexpored' is an anagram of 'PEROXIDE'.
(Other definitions for peroxide that I've seen before include "Powerful bleaching agent" , "See 8" , "Hair-bleaching fluid" , "Hair treatment" , "Chemical used to bleach hair" .)