Moved fast, say, on return in large open area (5)
I believe the answer is:
range
'large open area' is the definition.
(range can mean an open area of land)
'moved fast say on return' is the wordplay.
'moved fast' becomes 'ran' (I've seen this in another clue).
'say' becomes 'eg' (both can mean 'for example').
'on return' is a reversal indicator.
'eg' back-to-front is 'ge'.
'ran'+'ge'='RANGE'
'in' is the link.
(Other definitions for range that I've seen before include "Oven" , "Roam" , "Limits the area" , "spectrum" , "Compass - scope" .)