Use Bob's lad devised for instrument (6,4)
I believe the answer is:
double bass
'instrument' is the definition.
(double bass is a kind of instrument)
'use bob's lad devised' is the wordplay.
'devised' is an anagram indicator.
'use'+'bobs'+'lad'='usebobslad'
'usebobslad' with letters rearranged gives 'DOUBLE-BASS'.
'for' acts as a link.
(Other definitions for double bass that I've seen before include "... as part of orchestra" , "Stringed instrument" , "Musical instrument" , "One taking a bow" , "Low-pitched string instrument" .)