Private soldier in rock opera (5)
I believe the answer is:
tommy
This clue is a double definition.
'private soldier' is the first definition.
(I've seen this before)
'rock opera' is the second definition.
(I know that Tommy is a rock opera)
'in' acts as a link.
(Other definitions for tommy that I've seen before include "British soldier (informal)" , "Private soldier (slang)" , "British private soldier (colloq.)" , "Private in the Army - kind of gun" , "Doubtful apostle could be so familiar" .)