A cart drawn up on outskirts of Grasmere, distance measured (7)
I believe the answer is:
yardage
'distance measured' is the definition.
'a cart drawn up on outskirts of grasmere' is the wordplay.
'cart' becomes 'dray' (a cart without sides for delivering heavy loads).
'drawn up' says the letters should be written backwards.
'on' is a charade indicator (letters next to each other).
'outskirts of' suggests removing the centre.
'grasmere' with its centre removed is 'ge'.
'a'+'dray'='adray'
'adray' backwards is 'yarda'.
'yarda'+'ge'='YARDAGE'
(Other definitions for yardage that I've seen before include "Distance (eg in golf)" , "What a caddy should know" , "charge for using court" , "Distance in three-foot units" , "Distance - day rage (anag)" .)