Emperor's beginning to have stroke in this Roman livery (7)
I believe the answer is:
hepatic
'livery' is the definition.
(I've seen this before)
'emperor's beginning to have stroke in this roman' is the wordplay.
'beginning to' indicates taking the first letters.
'have' means one lot of letters go next to another.
'stroke' becomes 'pat' (pat can mean to stroke or touch).
'in' indicates putting letters inside.
'this roman' becomes 'hic' ('here' in Latin).
The first letter of 'emperors' is 'e'.
'e'+'pat'='epat'
'epat' placed within 'hic' is 'HEPATIC'.
(Other definitions for hepatic that I've seen before include "Livery" , "Pertaining to, or affecting, the liver or liverwort" , "brownish-red" , "of an organ" , "Relating to the liver" .)