Run over (5)
I believe this clue is a double definition.
'run' is the first definition.
(cricket run)
'over' is the second definition.
(extra can mean left over)
(Other definitions for extra that I've seen before include "Taxer (anag.)" , "Another" , "Additional - bye" , "he plays his part" , "One playing small part" .)
'run' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'over' is the wordplay.
I cannot quite see how this works, but
'over' could be 're' and 're' is located in the answer.
The remaining letters 'air' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?