Bother to locate extremities with instrument (5)
I believe the answer is:
bugle
'instrument' is the definition.
(bugle is a kind of instrument)
'bother to locate extremities' is the wordplay.
'bother' becomes 'bug' (I've seen this in another clue).
'extremities' says to hollow out the word (remove centre letters).
'locate' with its middle taken out is 'le'.
'bug'+'le'='BUGLE'
'with' is the link.
(Other definitions for bugle that I've seen before include "Bit of brass" , "Trumpet-like instrument" , "'Last Post' instrument" , "An army trumpet" , "Brass instrument without valves" .)