“Old jalopy” does frighten and upset a bit (10)
I believe the answer is:
rattletrap
'old jalopy' is the definition.
'rattletrap' can be an answer for 'jalopy' (I've seen this before). I'm unsure of the 'old' bit.
'frighten and upset a bit' is the wordplay.
'frighten' becomes 'rattle' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'upset' is a reversal indicator.
'a bit' becomes 'part' (both can mean a piece of something).
'part' in reverse letter order is 'trap'.
'rattle'+'trap'='RATTLETRAP'
'does' acts as a link.
Can you help me to learn more?
(Other definitions for rattletrap that I've seen before include "Old car" , "old vehicle" , "Rickety vehicle" , "jalopy" , "Vehicle, wobbly" .)