Perfectly straight (5)
I believe the answer is:
plumb
(Other definitions for plumb that I've seen before include "Measure the depth of water" , "Lead weight; exactly" , "Take soundings at sea" , "For Americans, quite" , "Utterly" .)
I believe the answer is:
plumb
(Other definitions for plumb that I've seen before include "Measure the depth of water" , "Lead weight; exactly" , "Take soundings at sea" , "For Americans, quite" , "Utterly" .)