Confounded girl interrupting father (6)
I believe the answer is:
dashed
'confounded' is the definition.
(I've seen this before)
'girl interrupting father' is the wordplay.
'girl' becomes 'she'.
'interrupting' indicates putting letters inside.
'father' becomes 'dad' (informal term for father).
'she' put within 'dad' is 'DASHED'.
(Other definitions for dashed that I've seen before include "completely spoiled" , "Ran quickly, rushed" , "Jolly" , "Flaming" , "as are semi-finalist and runner-up?" .)