Universal start of sale promotion for Marvel productions? (6)

I believe the answer is:

cosmic

'universal' is the definition.
(relating to the universe)

I cannot understand how the remainder of the clue works.

(Other definitions for cosmic that I've seen before include "Grandiose" , "Of the universe, infinite" , "Large -- universal" , "To do with the whole universe" , "Johann Sebastian --" .)

I've seen this clue in The Guardian.

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