After parking beside one, don't do anything yet (8)
I believe the answer is:
postpone
'don't do anything yet' is the definition.
I can't judge whether this defines the answer.
'after parking beside one' is the wordplay.
'after' becomes 'post' (prefix meaning after, eg post-war).
'parking' becomes 'p' (abbreviation on road signs).
'beside' means one lot of letters go next to another (I've seen this in other clues).
'post'+'p'+'one'='POSTPONE'
Can you help me to learn more?
(Other definitions for postpone that I've seen before include "Put off till another time" , "Put off, defer" , "'Put off, delay (8)'" , "'Hold over, defer (8)'" , "Put off until future date" .)