Two containers make a musical instrument (10)
I believe the answer is:
kettledrum
'a musical instrument' is the definition.
(kettledrum is a kind of musical instrument)
'two containers' is the wordplay.
'two containers' can mean two replacements for 'container'.
'container' becomes 'kettle' (kettle is a kind of container).
'container' becomes 'drum' (as in an oil drum).
'kettle'+'drum'='KETTLEDRUM'
'make' is the link.
(Other definitions for kettledrum that I've seen before include "one beaten with sticks" , "17 instrument" , "Part of kitchen" , "thing to produce tattoo" , "Orchestral instrument" .)