Slippery viper, I'm holding it: simple! (9)
I believe the answer is:
primitive
'simple' is the definition.
(thesaurus)
'slippery viper i'm holding it' is the wordplay.
'slippery' indicates anagramming the letters (I've seen this in other clues).
'holding' means one lot of letters goes inside another.
'viper'+'im'='viperim'
'viperim' with letters rearranged gives 'primive'.
'primive' placed around 'it' is 'PRIMITIVE'.
(Other definitions for primitive that I've seen before include "Characteristic of early uncivilised period" , "Undeveloped, rudimentary" , "With basic level of comfort" , "Early - simple - crude" , "extremely basic" .)