Weed out, taking back LSD, E and speed (9)
I believe the answer is:
eradicate
'weed out' is the definition.
(thesaurus)
'taking back lsd e and speed' is the wordplay.
'taking' is an insertion indicator.
'back' says the letters should be written backwards.
'lsd' becomes 'acid' (synonyms).
'and' means one lot of letters go next to another.
'speed' becomes 'rate' (the speed at which something happens).
'acid' backwards is 'dica'.
'e'+'rate'='erate'
'dica' placed inside 'erate' is 'ERADICATE'.
(Other definitions for eradicate that I've seen before include "Kill" , "Scotch" , "Exterminate, extinguish" , "scratch" , "Expunge" .)