Uncovered roux in large enough container (7)
I believe the answer is:
ampoule
'container' is the definition.
(ampoule is a kind of container)
'uncovered roux in large enough' is the wordplay.
'uncovered' indicates the central letters.
'in' is an insertion indicator.
'large enough' becomes 'ample' (I've seen this before).
The middle of 'roux' is 'ou'.
'ou' going within 'ample' is 'AMPOULE'.
(Other definitions for ampoule that I've seen before include "Vessel holding liquid for injection" , "Sealed glass container for injection solution" , "Capsule containing injection dose" , "Glass container for hypodermic dose" , "Glass capsule" .)