Wayward glance is a pain killer (9)
I believe the answer is:
analgesic
'pain killer' is the definition.
(thesaurus)
'wayward glance is a' is the wordplay.
'wayward' is an anagram indicator (wayward means out of control or chaotic).
'glance'+'is'+'a'='glanceisa'
'glanceisa' is an anagram of 'ANALGESIC'.
(Other definitions for analgesic that I've seen before include "result is soothing" , "number" , "Anodyne" , "Pain-killer" , "Relieving pain" .)