Periodical suffering, lumbago's back! (5)
I believe the answer is:
hello
'periodical' is the definition.
(Hello is a celebrity magazine)
'suffering lumbago's back' is the wordplay.
'suffering' becomes 'hell' (hell can mean a terrible ordeal).
'back' indicates one should take the final letters (the letter at the back).
The final letter of 'lumbago' is 'o'.
'hell'+'o'='HELLO'
(Other definitions for hello that I've seen before include "Meeting greeting" , "Common greeting as on phone" , "royals dominate its pages?" , "Look at that" , "Welcome" .)