Odd job with an instrument (5)
I believe the answer is:
banjo
'instrument' is the definition.
(I know that banjo is a type of stringed instrument)
'odd job with an' is the wordplay.
'odd' indicates an anagram.
'with' is an insertion indicator.
'job' with letters rearranged gives 'bjo'.
'bjo' placed around 'an' is 'BANJO'.
(Other definitions for banjo that I've seen before include "Relative of the guitar" , "String instrument" , "Stringed instrument like guitar with round body" , "strumming instrument" , "Softly (music)" .)