Girl and writer run off to marry (8)
I believe the answer is:
penelope
'girl' is the definition.
'writer run off to marry' is the wordplay.
'writer' becomes 'pen' (something which writes).
'run off to marry' becomes 'elope' (I've seen this in another clue).
'pen'+'elope'='PENELOPE'
'and' is the link.
(Other definitions for penelope that I've seen before include "Odysseus's wife" , "Girl's name" , "Mrs Odysseus" , "Ulysses' faithful wife" , "Woman" .)