... strangely ensured it ran wild (12)
I believe the answer is:
unrestrained
'wild' is the definition.
('unrestrained' can be a synonym of 'wild')
'strangely ensured it ran' is the wordplay.
'strangely' indicates anagramming the letters.
'ensured'+'it'+'ran'='ensureditran'
'ensureditran' with letters rearranged gives 'UNRESTRAINED'.
(Other definitions for unrestrained that I've seen before include "Not held back" , "Unchecked" , "Wild" , "Not restricted" , "spreading everywhere?" .)