Measure bridge (4)
I believe the answer is:
span
I believe this clue is a double definition.
'measure' is the first definition.
(span is a kind of measure)
'bridge' is the second definition.
(synonyms)
(Other definitions for span that I've seen before include "Bridge made of pans" , "Steeleye ___ , British folk-rock band, formed 1969" , "too short for the foot" , "Section of bridge" , "Width of wings" .)