Admirer of procrastinator's mantra? (8)
I believe the answer is:
idolater
'admirer' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
(Other definitions for idolater that I've seen before include "Tailored for image worshipper" , "I love a religious image" , "I'm devoted to my image" , "Tailored like pagan worshipper" , "False worshipper; tailored (anag.)" .)