Old boxer appearing regularly in tabloid (3)
I believe the answer is:
ali
'old boxer' is the definition.
(Muhammad Ali)
'regularly in tabloid' is the wordplay.
'regularly in' means one should take alternating letters.
The alternating letters of 'tabloid' are 'ALI'.
'appearing' acts as a link.
(Other definitions for ali that I've seen before include "Mohammad . . ., . . . Hewson" , "Champion of ring" , "Muhammad ___ (or MacGraw?)" , "Ring' specialist" , "Son-in-law to Muhammad" .)