Catch bout involving start of bilious indigestion (9)
I believe the answer is:
heartburn
'indigestion' is the definition.
(I've seen this before)
'catch bout involving start of bilious' is the wordplay.
'catch' becomes 'hear' (I've seen this before**).
'bout' becomes 'turn' ('turn' can be a synonym of 'bout').
'involving' is an insertion indicator.
'start of' says to take the initial letters.
The first letter of 'bilious' is 'b'.
'turn' placed around 'b' is 'tburn'.
'hear'+'tburn'='HEARTBURN'
(Other definitions for heartburn that I've seen before include "minor ailment" , "You'll get feeling of discomfort" , "Painful sensation" , "Indigestion of cardiac origin?" , "Hot sensation in lower chest from indigestion" .)