Lizard I left is found in lounge (8)
I believe the answer is:
basilisk
'lizard' is the definition.
(mythical lizard creature)
'i left is found in lounge' is the wordplay.
'left' becomes 'l' (common abbreviation).
'found in' is an insertion indicator.
'lounge' becomes 'bask' (both can mean to laze around).
'i'+'l'+'is'='ilis'
'ilis' placed into 'bask' is 'BASILISK'.
(Other definitions for basilisk that I've seen before include "Mythical reptile said to cause death by its breath or glance" , "Mythical monster" , "Mythic serpent able to kill with its breath or glance" , "Legendary creature with killing glance" , "Lethal, legendary serpent" .)