Did nothing about Geordie endlessly playing musical instrument (10)
I believe the answer is:
didgeridoo
'musical instrument' is the definition.
(I've seen this before)
'did nothing about geordie endlessly playing' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'about' means one lot of letters goes inside another.
'endlessly' means to remove the last letter.
'playing' is an anagram indicator.
'did'+'o'='dido'
'geordie' with its last letter removed is 'geordi'.
'geordi' with letters rearranged gives 'gerido'.
'dido' placed around 'gerido' is 'DIDGERIDOO'.
(Other definitions for didgeridoo that I've seen before include "wind instrument" , "Aboriginal instrument" , "One Aussies played" , "musical instrument" , "It's used in Bush" .)