Extend over (4)
I believe the answer is:
span
'extend over' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for span that I've seen before include "Bridge - spick and ___" , "Bridge or range" , "Interval; pair of yoked oxen" , "Extent - 9 inches" , "Extend from end to end, say bridge" .)