Bow of rescue vessel in the sound (3)
I believe the answer is:
arc
'bow' is the definition.
(both can mean a curve)
'rescue vessel in the sound' is the wordplay.
'rescue vessel' becomes 'ark' (rescue ship in the Bible).
'in the sound' indicates a 'sounds like' (homophone) clue.
'ark' sounds like 'ARC'.
'of' is the link.
(Other definitions for arc that I've seen before include "Electrical spark" , "A curve; a discharge" , "Part of circle; discharge" , "Part of a circle's circumference" , "Don't go straight" .)