An insect after cheese, in short (7)
I believe the answer is:
briefly
'in short' is the definition.
(synonyms)
'an insect after cheese' is the wordplay.
'an insect' becomes 'fly' (fly is a kind of insect).
'after' says to put letters next to each other.
'cheese' becomes 'brie' (Brie is an example).
'fly' put after 'brie' is 'BRIEFLY'.
(Other definitions for briefly that I've seen before include "In a nutshell" , "Cursorily" , "Concisely" , "In a few words" , "For a short time" .)