Better half of pop song a hit in language of SW India (9)
I believe the answer is:
malayalam
'language of sw india' is the definition.
'Malayalam' can be an answer for 'language' (Malayalam is an example). I'm not certain of the 'of sw india' bit.
'better half of pop song a hit' is the wordplay.
'better half of pop' becomes 'ma' (I can't explain this - if you can you should give a lot more credence to this answer).
'song' becomes 'lay' (poetic term for a song).
'hit' becomes 'lam' (to 'lam' means to hit hard).
'ma'+'lay'+'a'+'lam'='MALAYALAM'
'in' is the link.
Can you help me to learn more?
(Other definitions for malayalam that I've seen before include "Indian language" , "Palindromic Far East language" , "Language we don't often hear" .)