Friend, without hesitation, approaches a metal instrument that's feared by sailors? (7,8)
I believe the answer is:
bermuda triangle
'that's feared by sailors?' is the definition.
'friend without hesitation approaches a metal instrument' is the wordplay.
'friend' becomes 'bud' (shortly for buddy).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'hesitation' becomes 'erm' (**).
'approaches' says to put letters next to each other.
'metal instrument' becomes 'triangle'.
'bud' enclosing 'erm' is 'bermud'.
'bermud'+'a'+'triangle'='BERMUDA TRIANGLE'
(Other definitions for bermuda triangle that I've seen before include "associated with disappearing craft?" , "notorious danger area?" , "Area of mystery" , "mysterious place" , "Place where ships have been mysteriously lost" .)