Put mares out towards spring. perhaps (8)
I believe the answer is:
upstream
'towards spring perhaps' is the definition.
(heading towards a spring or stream)
'put mares out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'put'+'mares'='putmares'
'putmares' with letters rearranged gives 'UPSTREAM'.
(Other definitions for upstream that I've seen before include "at an earlier stage in process" , "Towards (river's) source" , "Facing current" , "away from estuary?" , "opposing current tendencies" .)