Minor riot lad stirred, snaring unknown reptile (7,6)
I believe the answer is:
monitor lizard
'reptile' is the definition.
(monitor lizard is a kind of reptile)
'minor riot lad stirred snaring unknown' is the wordplay.
'stirred' indicates an anagram.
'snaring' indicates putting letters inside.
'unknown' becomes 'z' (algebra).
'minor'+'riot'+'lad'='minorriotlad'
'minorriotlad' is an anagram of 'monitorliard'.
'monitorliard' enclosing 'z' is 'MONITOR LIZARD'.
(Other definitions for monitor lizard that I've seen before include "Reptile" , "Beast" .)