Display struggle for breath over time (7)
I believe the answer is:
pageant
'display' is the definition.
(thesaurus)
'struggle for breath over time' is the wordplay.
'struggle for breath' becomes 'pant' (to pant is to struggle for breath).
'over' means one lot of letters goes inside another.
'time' becomes 'age' (an age is a period of time).
'pant' going around 'age' is 'PAGEANT'.
(Other definitions for pageant that I've seen before include "Neat gap for colourful spectacle" , "Dramatic performance" , "Colourful display or parade" , "Costumed procession" , "Magnificent parade" .)