In Morocco's mostly an all-star display (6)
I believe the answer is:
cosmos
'all-star display' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'in morocco's mostly an' is the wordplay.
'in' says the answer is hidden in the clue.
'COSMOS' can be found hidden inside 'moroccos mostly an'.
Can you help me to learn more?
(Other definitions for cosmos that I've seen before include "The universe - a daisy" , "Everything that exists" , "Universe seen as a whole" , "The entire universe." , "Universe as an ordered whole" .)