Poet, for example, among fifth-rate celebrities (7)
I believe the answer is:
elegist
'poet' is the definition.
(I know that elegist is a type of poet)
'example among fifth-rate celebrities' is the wordplay.
'example' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'among' is an insertion indicator.
'fifth-rate' becomes 'E' (fifth worst category).
'celebrities' becomes 'list' (I am not sure about this - if you are sure you should believe this answer much more).
'e'+'list'='elist'
'eg' put into 'elist' is 'ELEGIST'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for elegist that I've seen before include "Writer of reflective poems" , "Poet, e.g. Gray" , "serious linesman" , "Kind of writer" , "Composer of mournful songs" .)