Girl to run away with writer (8)
I believe the answer is:
penelope
'girl' is the definition.
'run away with writer' is the wordplay.
'run away' becomes 'elope' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'writer' becomes 'pen' (something which writes).
'elope' put after 'pen' is 'PENELOPE'.
'to' is the link.
(Other definitions for penelope that I've seen before include "Woman" , "Mrs Odysseus" , "Wife of Odysseus or Ulysses" , "Ulysses' faithful wife" , "girl" .)