Happen to firm up with copper at top of road (5)
I believe the answer is:
occur
'happen' is the definition.
(I know that happen is a more specific form of happen)
'firm up with copper at top of road' is the wordplay.
'firm up' becomes 'oc' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'copper' becomes 'Cu' (Cu is the chemical symbol for copper).
'at' is a charade indicator (letters next to each other).
'top of' says to take the initial letters.
The initial letter of 'road' is 'r'.
'oc'+'cu'+'r'='OCCUR'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for occur that I've seen before include "exist" , "Happen, transpire" , "Spring to mind" , "appear" , "Go on" .)