Must argue about celebrity (4)
I believe the answer is:
star
'celebrity' is the definition.
(a star is a celebrity or famous person)
'must argue about' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'STAR' is hidden in the letters of 'must argue'.
(Other definitions for star that I've seen before include "Celeb" , "top player" , "Brilliant performer?" , "Polaris, for example" , "Top-of-the-bill artist" .)