Dope fixing a steed (6)
I believe the answer is:
sedate
'dope' is the definition.
(thesaurus)
'fixing a steed' is the wordplay.
'fixing' indicates an anagram.
'a'+'steed'='asteed'
'asteed' with letters rearranged gives 'SEDATE'.
(Other definitions for sedate that I've seen before include "Calm, sober" , "Quiet and rather dull" , "Seated strangely in a demure sort of way" , "Calm, unhurried" , "Staid and sober" .)