Girl has old rope (5)
I believe the answer is:
lasso
'rope' is the definition.
(lassoing is a kind of roping)
'girl has old' is the wordplay.
'girl' becomes 'lass' (lass can informally mean a girl).
'has' means one lot of letters go next to another.
'old' becomes 'o' (abbreviation).
'lass'+'o'='LASSO'
(Other definitions for lasso that I've seen before include "Catch (steers) with a rope" , "Cowboy's rope with sliding noose" , "something to catch beast liable to run off" , "One may be caught by this" , "use one for catching cattle" .)