Indian father is in pain (6)
I believe the answer is:
apache
'indian' is the definition.
(Apache is an example)
'father is in pain' is the wordplay.
'father' becomes 'pa' (pa is a kind of father).
'is in' indicates putting letters inside.
'pain' becomes 'ache' (ache is a kind of pain).
'pa' going inside 'ache' is 'APACHE'.
(Other definitions for apache that I've seen before include "language" , "US native" , "Parisian gangster" , "A peach of an Indian tribe?" , "N American Indian tribe or old Paris ruffian" .)