Secretive celebrity's large body not evident to viewers (4)

I think it could be either:

Which length description are you looking for?:

4,4

dark

'secretive' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for dark that I've seen before include "Black, perhaps - night" , "Sinister - evening" , "Nightfall; without light" , "Dimly lit" , "Obscure - sinister" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app