Jack up part of car that’s stuck on the road (6)
I believe the answer is:
tarmac
'car that's stuck on the road' is the definition.
I can't tell whether this defines the answer.
'jack up part' is the wordplay.
'jack' becomes 'tar' (both are informal terms for sailor).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'part' becomes 'cam' (I have seen 'Part of engine' mean 'cam' so perhaps 'part' could also mean 'cam').
'cam' reversed gives 'mac'.
'tar'+'mac'='TARMAC'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for tarmac that I've seen before include "Road-surfacing material" , "Airport runway(s)" , "Surface material of tar and broken stone" , "Airport runway surface" , "short runway, perhaps" .)