Left old rocker not feeling great, apparently (6)
I believe the answer is:
parted
'left' is the definition.
(parting is a kind of leaving)
'old rocker not feeling great apparently' is the wordplay.
I cannot really see how this works, but
'rocker' could be 'ted' (member of the Teddy boy subculture) and 'ted' is found within the answer.
The remaining letters 'par' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for parted that I've seen before include "Divided or separated" , "Divided, broken" , "Divided and said goodbye" , "One's hair might be" , "Split up, separated" .)