When duff gen comes in, she's responsible (5)
I believe the answer is:
agnes
'in she's responsible' is the definition.
I can't judge whether this defines the answer.
'when duff gen' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'gen' is 'gne' which is located in the answer.
'when' could be 'as' (eg 'when I walked' means 'as I walked') and 'as' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'comes' acts as a link.
Can you help me to learn more?
(Other definitions for agnes that I've seen before include "Tube for cables" , "David's second wife" , "Girl's name" , "Scandinavian singer" , "The Eve of St. - (Keats)" .)