Fine weather for an Asian mathematician, perhaps (6,6)
I believe the answer is:
indian summer
'fine weather' is the definition.
(fine weather in autumn)
'an asian mathematician perhaps' is the wordplay.
'an asian' becomes 'Indian' (India is in Asia).
'mathematician perhaps' becomes 'summer' (someone who does sums).
'indian'+'summer'='INDIAN SUMMER'
'for' is the link.
(Other definitions for indian summer that I've seen before include "Welcome warmth" , "Unexpectedly warm period late in the year" , "counter-wallah" , "Autumn warm spell" , "Late heatwave" .)