The girl had brought an action (4)
I believe the answer is:
sued
'brought an action' is the definition.
(I've seen this in another clue)
'the girl had' is the wordplay.
'the girl' becomes 'sue' (girl's name).
'had' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc).
'sue'+'d'='SUED'
(Other definitions for sued that I've seen before include "Prosecuted" , "taken to court" , "Started legal proceedings against (someone)" , "Took legal action against" , "Brought an action against" .)