Runner, girl, not finishing run (7)
I believe the answer is:
harrier
'runner' is the definition.
(I've seen this before)
'girl not finishing run' is the wordplay.
I cannot quite see how this works, but
'girl' could be 'harrie' and 'harrie' is present in the answer.
'run' could be 'r' (cricket abbreviation) and 'r' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for harrier that I've seen before include "Hound; bird of prey" , "Long distance runner" , "Short-winged hawk" , "Hare hound" , "jump jet" .)