Great instrument, short of parts (10)
I believe the answer is:
thundering
'great' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'instrument short of parts' is the wordplay.
'instrument' becomes 'thing' (I can't justify this - if you can you should believe this answer much more).
'short of' becomes 'under' (eg short of t0 means under t0).
'parts' indicates putting letters inside (in the sense of cuts or separates).
'thing' going around 'under' is 'THUNDERING'.
Can you help me to learn more?
(Other definitions for thundering that I've seen before include "Tremendous" , "Making a loud noise" .)