Rushed to treat damp steed (9)
I believe the answer is:
stampeded
'rushed' is the definition.
(to stampede is to rush or charge)
'treat damp steed' is the wordplay.
'treat' indicates an anagram.
'damp'+'steed'='dampsteed'
'dampsteed' anagrammed gives 'STAMPEDED'.
'to' is the link.
(Other definitions for stampeded that I've seen before include "Dashed off" , "Together, quickly ran" , "rushed in panic" , "Rushed wildly" .)