Get right into a seat -- with legs thus? (9)
'legs thus?' is the definition.
I know nothing about this answer so I can't judge whether this works.
'get right into a seat' is the wordplay.
'get right' becomes 'r' (I've seen this in other clues).
'into' indicates putting letters inside.
'seat' becomes 'staddle' (I can't justify this - if you can you should believe this answer much more).
'r' going within 'astaddle' is 'ASTRADDLE'.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for astraddle that I've seen before include "with legs wide apart", "How the jockey wants to be", "Across", "With a leg on either side of (something)".)