Possible Clues:

• I'll make seat lower, retaining length
• Leather-worker not so happy about pound
• Leather worker requires small adjustable ladder
• Horse-seat maker
• One offering seat to sit on nags pathetic layabout -- not I
• One providing something to help a person sit up
• Senior, quaintly rotten inside, whose clients put something on the horses
• One who'd be less happy about minimal supply of leather?
• All this worker makes going on the horses?
• Tack supplier’s son finally fell, bitten by snake