Singing and shouting odds regularly inside (9)
I believe the answer is:
yodelling
'singing' is the definition.
'shouting odds regularly inside' is the wordplay.
'shouting' becomes 'yelling' (yelling is a kind of shouting).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'inside' means one lot of letters goes inside another.
The alternating letters of 'odds' are 'od'.
'yelling' going around 'od' is 'YODELLING'.
'and' is the link.
(Other definitions for yodelling that I've seen before include "making offpeak call" , "singing style" .)