Remains upright until they come to a stop (10)
I believe the answer is:
standstill
'to a stop' is the definition.
(standstill is a kind of stop)
'remains upright until' is the wordplay.
'remains upright' becomes 'stands' (I've seen this before).
'until' becomes 'till' (I've seen this in other clues).
'stands'+'till'='STANDSTILL'
'they come' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for standstill that I've seen before include "Complete stop" , "lack of movement" , "Situation without movement or activity" , "negation of motion" , "arrest" .)