Tool for workmen making bridge (7)
I believe the answer is:
spanner
I believe this is a double definition.
'tool for workmen' is the first definition.
(workmen might use a spanner)
'bridge' is the second definition.
(something which spans two points)
'making' acts as a link.
(Other definitions for spanner that I've seen before include "Tool for tightening or loosening" , "Hand tool to hold or twist" , "Bad thing to have in the works!" , "Nut-tightening tool" , "Nut tightener" .)