Girl involved in Indian nationalism (4)
I believe the answer is:
anna
'girl' is the definition.
'involved in indian nationalism' is the wordplay.
'involved in' indicates the answer is hidden within the clue.
'ANNA' can be found hidden inside 'indian nationalism'.
(Other definitions for anna that I've seen before include "Former one sixteenth of Rupee" , "- - Ford (TV)" , "Old foreign coin" , "-- Wintour, editor" , "Girl - old Indian coin" .)