Costume remaining the same (7)
I believe the answer is:
uniform
This could be a double definition.
'costume remaining' is the first definition.
'uniform' can be an answer for 'costume' (both can mean clothing). I am not certain of the 'remaining' bit.
'same' is the second definition.
(synonyms)
'the' acts as a link.
Can you help me to learn more?
(Other definitions for uniform that I've seen before include "Regular; clothing" , "Constant; outfit" , "The same throughout" , "Unvarying - work clothing" , "Consistent, unvarying" .)