Area covered by second best doctor on a temporary basis (7)
I believe the answer is:
stopgap
'on a temporary basis' is the definition.
(as in a stopgap measure)
'area covered by second best' is the wordplay.
'area' becomes 'gap' (I can't justify this - if you can you should give a lot more credence to this answer).
'covered by' means one lot of letters go next to another (on top of in a down clue).
'second' becomes 's' (common abbreviation).
'best' becomes 'top' (top can mean the very best).
's'+'top'='stop'
'gap' after 'stop' is 'STOPGAP'.
'doctor' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for stopgap that I've seen before include "caretaker" , "Temporary fix" , "Interim" , "Makeshift" , "Temporary expedient" .)