In building for horses, always open to influence (9)
I believe the answer is:
steerable
'open to influence' is the definition.
I can't judge whether this definition defines the answer.
'in building for horses always' is the wordplay.
'in' indicates putting letters inside.
'building for horses' becomes 'stable' (I've seen this before).
'always' becomes 'eer' (poetic way of saying ever).
'stable' enclosing 'eer' is 'STEERABLE'.
Can you help me to learn more?
(Another definition for steerable that I've seen is " amenable to guidance".)