Parking not bad up a terrace (3)
I believe the answer is:
kop
'a terrace' is the definition.
(type of terrace in football stadiums)
'parking not bad up' is the wordplay.
'parking' becomes 'p'.
'not bad' becomes 'ok'.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'p'+'ok'='pok'
'pok' in reverse letter order is 'KOP'.
(Other definitions for kop that I've seen before include "High football terrace" , "football terraces" , "Football stand" .)