G'day! Swap taps for some strings (5)
I believe the answer is:
cello
'some strings' is the definition.
I cannot understand how the rest of the clue works.
(Other definitions for cello that I've seen before include "It's bigger than a viola, but smaller than a double bass" , "Bass stringed instrument" , "Viola's bigger brother?" , "large-scale fiddle" , "Musical instrument like large violin held between knees" .)